diff --git a/Cargo.lock b/Cargo.lock
index a6b5a9f8..dae60f3e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1780,7 +1780,6 @@ dependencies = [
  "serde",
  "serde_json",
  "serde_yaml_ng",
- "temp-env",
  "tempfile",
  "tokio",
  "url",
@@ -3108,7 +3107,6 @@ version = "0.3.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "96374855068f47402c3121c6eed88d29cb1de8f3ab27090e273e420bdabcf050"
 dependencies = [
- "futures",
  "parking_lot",
 ]
 
diff --git a/crates/mergify-ci/Cargo.toml b/crates/mergify-ci/Cargo.toml
index 4bcb2609..562bc9eb 100644
--- a/crates/mergify-ci/Cargo.toml
+++ b/crates/mergify-ci/Cargo.toml
@@ -30,7 +30,6 @@ url = { workspace = true }
 [dev-dependencies]
 mergify-test-support = { path = "../mergify-test-support" }
 tempfile = { workspace = true }
-temp-env = { workspace = true, features = ["async_closure"] }
 tokio = { workspace = true }
 wiremock = { workspace = true }
 
diff --git a/crates/mergify-ci/src/detector.rs b/crates/mergify-ci/src/detector.rs
index b2e020c8..56001a1a 100644
--- a/crates/mergify-ci/src/detector.rs
+++ b/crates/mergify-ci/src/detector.rs
@@ -6,7 +6,7 @@
 //! Rust commands are mirrored; the rest stays in Python until its
 //! command is ported.
 
-use std::env;
+use mergify_core::env;
 
 use mergify_core::CliError;
 use mergify_core::auth;
@@ -38,16 +38,16 @@ impl CIProvider {
 
 #[must_use]
 pub fn get_ci_provider() -> Option<CIProvider> {
-    if env::var("JENKINS_URL").is_ok_and(|v| !v.is_empty()) {
+    if env::var_non_empty("JENKINS_URL").is_some() {
         return Some(CIProvider::Jenkins);
     }
-    if env::var("GITHUB_ACTIONS").as_deref() == Ok("true") {
+    if env::var("GITHUB_ACTIONS").as_deref() == Some("true") {
         return Some(CIProvider::GithubActions);
     }
-    if env::var("CIRCLECI").as_deref() == Ok("true") {
+    if env::var("CIRCLECI").as_deref() == Some("true") {
         return Some(CIProvider::CircleCi);
     }
-    if env::var("BUILDKITE").as_deref() == Ok("true") {
+    if env::var("BUILDKITE").as_deref() == Some("true") {
         return Some(CIProvider::Buildkite);
     }
     None
@@ -58,7 +58,7 @@ pub fn get_ci_provider() -> Option<CIProvider> {
 /// repository URL into ``owner/repo``. Returns ``None`` when the var
 /// is unset or the value doesn't parse.
 fn get_github_repository_from_env(env_name: &str) -> Option<String> {
-    let raw = env::var(env_name).ok()?;
+    let raw = env::var(env_name)?;
     parse_repository_url(&raw)
 }
 
@@ -151,7 +151,7 @@ pub fn split_owner_repo(value: &str) -> Result<(&str, &str), CliError> {
 #[must_use]
 pub fn get_github_repository() -> Option<String> {
     match get_ci_provider()? {
-        CIProvider::GithubActions => env::var("GITHUB_REPOSITORY").ok().filter(|s| !s.is_empty()),
+        CIProvider::GithubActions => env::var_non_empty("GITHUB_REPOSITORY"),
         CIProvider::CircleCi => get_github_repository_from_env("CIRCLE_REPOSITORY_URL"),
         CIProvider::Jenkins => get_github_repository_from_env("GIT_URL"),
         CIProvider::Buildkite => get_github_repository_from_env("BUILDKITE_REPO"),
@@ -199,9 +199,13 @@ pub fn get_github_pull_request_number() -> Result<Option<u64>, CliError> {
     match get_ci_provider() {
         Some(CIProvider::GithubActions) => read_github_event_pull_request_number(),
         Some(CIProvider::Buildkite) => match env::var("BUILDKITE_PULL_REQUEST") {
-            Ok(pr) if !pr.is_empty() && pr != "false" => pr.parse::<u64>().map(Some).map_err(|e| {
-                CliError::Configuration(format!("BUILDKITE_PULL_REQUEST is not an integer: {e}"))
-            }),
+            Some(pr) if !pr.is_empty() && pr != "false" => {
+                pr.parse::<u64>().map(Some).map_err(|e| {
+                    CliError::Configuration(format!(
+                        "BUILDKITE_PULL_REQUEST is not an integer: {e}"
+                    ))
+                })
+            }
             _ => Ok(None),
         },
         _ => Ok(None),
@@ -216,7 +220,7 @@ fn read_github_event_pull_request_number() -> Result<Option<u64>, CliError> {
     // [`read_github_event_pull_request_head_sha`]) stays lenient
     // because every one of its callers has somewhere to go without
     // an answer.
-    let Some(event_path) = env::var("GITHUB_EVENT_PATH").ok().filter(|s| !s.is_empty()) else {
+    let Some(event_path) = env::var_non_empty("GITHUB_EVENT_PATH") else {
         return Ok(None);
     };
     let content = match std::fs::read_to_string(&event_path) {
@@ -276,8 +280,8 @@ pub fn get_github_pull_request_head_sha() -> Option<String> {
         // Buildkite and CircleCI both build a pull request from its head
         // commit, so their revision var *is* that head (`git_refs` reads
         // `BUILDKITE_COMMIT` for the same purpose).
-        CIProvider::Buildkite => non_empty_env("BUILDKITE_COMMIT"),
-        CIProvider::CircleCi => non_empty_env("CIRCLE_SHA1"),
+        CIProvider::Buildkite => env::var_non_empty("BUILDKITE_COMMIT"),
+        CIProvider::CircleCi => env::var_non_empty("CIRCLE_SHA1"),
         CIProvider::Jenkins => None,
     }?;
     is_sha1_object_name(&sha).then_some(sha)
@@ -310,19 +314,18 @@ pub fn get_pipeline_name() -> Option<String> {
         CIProvider::Buildkite => "BUILDKITE_PIPELINE_SLUG",
         CIProvider::CircleCi => return None,
     };
-    non_empty_env(var)
+    env::var_non_empty(var)
 }
 
 /// `cicd.pipeline.task.name` — the job within a pipeline.
 #[must_use]
 pub fn get_job_name() -> Option<String> {
     match get_ci_provider()? {
-        CIProvider::GithubActions => non_empty_env("GITHUB_JOB"),
-        CIProvider::CircleCi => non_empty_env("CIRCLE_JOB"),
-        CIProvider::Jenkins => non_empty_env("JOB_NAME"),
-        CIProvider::Buildkite => {
-            non_empty_env("BUILDKITE_LABEL").or_else(|| non_empty_env("BUILDKITE_STEP_KEY"))
-        }
+        CIProvider::GithubActions => env::var_non_empty("GITHUB_JOB"),
+        CIProvider::CircleCi => env::var_non_empty("CIRCLE_JOB"),
+        CIProvider::Jenkins => env::var_non_empty("JOB_NAME"),
+        CIProvider::Buildkite => env::var_non_empty("BUILDKITE_LABEL")
+            .or_else(|| env::var_non_empty("BUILDKITE_STEP_KEY")),
     }
 }
 
@@ -334,10 +337,10 @@ pub fn get_head_ref_name() -> Option<String> {
             // GitHub Actions sets `GITHUB_HEAD_REF` only on PR
             // events. Fall back to `GITHUB_REF_NAME` everywhere
             // else (the bare branch name, not `<pr#>/merge`).
-            non_empty_env("GITHUB_HEAD_REF").or_else(|| non_empty_env("GITHUB_REF_NAME"))
+            env::var_non_empty("GITHUB_HEAD_REF").or_else(|| env::var_non_empty("GITHUB_REF_NAME"))
         }
-        CIProvider::CircleCi => non_empty_env("CIRCLE_BRANCH"),
-        CIProvider::Jenkins => non_empty_env("GIT_BRANCH").map(|raw| {
+        CIProvider::CircleCi => env::var_non_empty("CIRCLE_BRANCH"),
+        CIProvider::Jenkins => env::var_non_empty("GIT_BRANCH").map(|raw| {
             // Jenkins' Git plugin sets `GIT_BRANCH` to
             // `<remote>/<branch>` (or `refs/heads/<branch>` when
             // the job's configured for a refspec). Strip the
@@ -350,7 +353,7 @@ pub fn get_head_ref_name() -> Option<String> {
             }
             raw
         }),
-        CIProvider::Buildkite => non_empty_env("BUILDKITE_BRANCH"),
+        CIProvider::Buildkite => env::var_non_empty("BUILDKITE_BRANCH"),
     }
 }
 
@@ -358,9 +361,9 @@ pub fn get_head_ref_name() -> Option<String> {
 #[must_use]
 pub fn get_base_ref_name() -> Option<String> {
     match get_ci_provider()? {
-        CIProvider::GithubActions => non_empty_env("GITHUB_BASE_REF"),
-        CIProvider::Jenkins => non_empty_env("CHANGE_TARGET"),
-        CIProvider::Buildkite => non_empty_env("BUILDKITE_PULL_REQUEST_BASE_BRANCH"),
+        CIProvider::GithubActions => env::var_non_empty("GITHUB_BASE_REF"),
+        CIProvider::Jenkins => env::var_non_empty("CHANGE_TARGET"),
+        CIProvider::Buildkite => env::var_non_empty("BUILDKITE_PULL_REQUEST_BASE_BRANCH"),
         CIProvider::CircleCi => None,
     }
 }
@@ -369,9 +372,9 @@ pub fn get_base_ref_name() -> Option<String> {
 #[must_use]
 pub fn get_cicd_pipeline_runner_name() -> Option<String> {
     match get_ci_provider()? {
-        CIProvider::GithubActions => non_empty_env("RUNNER_NAME"),
-        CIProvider::Jenkins => non_empty_env("NODE_NAME"),
-        CIProvider::Buildkite => non_empty_env("BUILDKITE_AGENT_NAME"),
+        CIProvider::GithubActions => env::var_non_empty("RUNNER_NAME"),
+        CIProvider::Jenkins => env::var_non_empty("NODE_NAME"),
+        CIProvider::Buildkite => env::var_non_empty("BUILDKITE_AGENT_NAME"),
         CIProvider::CircleCi => None,
     }
 }
@@ -382,10 +385,10 @@ pub fn get_cicd_pipeline_runner_name() -> Option<String> {
 #[must_use]
 pub fn get_cicd_pipeline_run_id() -> Option<String> {
     match get_ci_provider()? {
-        CIProvider::GithubActions => non_empty_env("GITHUB_RUN_ID"),
-        CIProvider::CircleCi => non_empty_env("CIRCLE_WORKFLOW_ID"),
-        CIProvider::Jenkins => non_empty_env("BUILD_ID"),
-        CIProvider::Buildkite => non_empty_env("BUILDKITE_BUILD_ID"),
+        CIProvider::GithubActions => env::var_non_empty("GITHUB_RUN_ID"),
+        CIProvider::CircleCi => env::var_non_empty("CIRCLE_WORKFLOW_ID"),
+        CIProvider::Jenkins => env::var_non_empty("BUILD_ID"),
+        CIProvider::Buildkite => env::var_non_empty("BUILDKITE_BUILD_ID"),
     }
 }
 
@@ -393,11 +396,11 @@ pub fn get_cicd_pipeline_run_id() -> Option<String> {
 #[must_use]
 pub fn get_cicd_pipeline_run_attempt() -> Option<u64> {
     match get_ci_provider()? {
-        CIProvider::GithubActions => non_empty_env("GITHUB_RUN_ATTEMPT")?.parse().ok(),
-        CIProvider::CircleCi => non_empty_env("CIRCLE_BUILD_NUM")?.parse().ok(),
+        CIProvider::GithubActions => env::var_non_empty("GITHUB_RUN_ATTEMPT")?.parse().ok(),
+        CIProvider::CircleCi => env::var_non_empty("CIRCLE_BUILD_NUM")?.parse().ok(),
         // Buildkite uses 0-indexed retries; add 1 so a fresh run
         // reads as attempt 1 (matching the GHA/CircleCI semantics).
-        CIProvider::Buildkite => non_empty_env("BUILDKITE_RETRY_COUNT")?
+        CIProvider::Buildkite => env::var_non_empty("BUILDKITE_RETRY_COUNT")?
             .parse::<u64>()
             .ok()
             .map(|n| n + 1),
@@ -409,7 +412,7 @@ pub fn get_cicd_pipeline_run_attempt() -> Option<u64> {
 #[must_use]
 pub fn get_cicd_pipeline_run_url() -> Option<String> {
     match get_ci_provider()? {
-        CIProvider::Buildkite => non_empty_env("BUILDKITE_BUILD_URL"),
+        CIProvider::Buildkite => env::var_non_empty("BUILDKITE_BUILD_URL"),
         _ => None,
     }
 }
@@ -420,9 +423,9 @@ pub fn get_cicd_pipeline_run_url() -> Option<String> {
 #[must_use]
 pub fn get_repository_url() -> Option<String> {
     match get_ci_provider()? {
-        CIProvider::Buildkite => non_empty_env("BUILDKITE_REPO"),
-        CIProvider::CircleCi => non_empty_env("CIRCLE_REPOSITORY_URL"),
-        CIProvider::Jenkins => non_empty_env("GIT_URL"),
+        CIProvider::Buildkite => env::var_non_empty("BUILDKITE_REPO"),
+        CIProvider::CircleCi => env::var_non_empty("CIRCLE_REPOSITORY_URL"),
+        CIProvider::Jenkins => env::var_non_empty("GIT_URL"),
         CIProvider::GithubActions => None,
     }
 }
@@ -444,19 +447,19 @@ pub fn get_repository_url() -> Option<String> {
 pub fn get_head_sha() -> Option<String> {
     match get_ci_provider()? {
         CIProvider::GithubActions => get_github_actions_head_sha(),
-        CIProvider::CircleCi => non_empty_env("CIRCLE_SHA1"),
-        CIProvider::Jenkins => non_empty_env("GIT_COMMIT"),
-        CIProvider::Buildkite => non_empty_env("BUILDKITE_COMMIT"),
+        CIProvider::CircleCi => env::var_non_empty("CIRCLE_SHA1"),
+        CIProvider::Jenkins => env::var_non_empty("GIT_COMMIT"),
+        CIProvider::Buildkite => env::var_non_empty("BUILDKITE_COMMIT"),
     }
 }
 
 fn get_github_actions_head_sha() -> Option<String> {
-    if env::var("GITHUB_EVENT_NAME").as_deref() == Ok("pull_request")
+    if env::var("GITHUB_EVENT_NAME").as_deref() == Some("pull_request")
         && let Some(sha) = read_github_event_pull_request_head_sha()
     {
         return Some(sha);
     }
-    non_empty_env("GITHUB_SHA")
+    env::var_non_empty("GITHUB_SHA")
 }
 
 /// Read `GITHUB_EVENT_PATH` and pluck the
@@ -475,7 +478,7 @@ fn read_github_event_pull_request_head_sha() -> Option<String> {
 }
 
 fn read_github_event_json() -> Option<serde_json::Value> {
-    let event_path = env::var("GITHUB_EVENT_PATH").ok()?;
+    let event_path = env::var("GITHUB_EVENT_PATH")?;
     if event_path.is_empty() {
         return None;
     }
@@ -483,10 +486,6 @@ fn read_github_event_json() -> Option<serde_json::Value> {
     serde_json::from_str(&content).ok()
 }
 
-fn non_empty_env(name: &str) -> Option<String> {
-    env::var(name).ok().filter(|s| !s.is_empty())
-}
-
 /// Branch the quarantine API should look up tests for. Mirrors
 /// Python's `get_tests_target_branch`: the PR base branch when
 /// available, otherwise the head branch — i.e. "the branch the
@@ -500,13 +499,12 @@ pub fn get_tests_target_branch() -> Option<String> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::testing::with_ci_env;
     use crate::testing::write_github_event;
 
     #[test]
     fn ci_provider_jenkins_takes_precedence() {
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("JENKINS_URL", Some("http://jenkins")),
                 ("GITHUB_ACTIONS", Some("true")),
                 ("CIRCLECI", Some("true")),
@@ -520,15 +518,15 @@ mod tests {
 
     #[test]
     fn ci_provider_returns_none_when_unset() {
-        with_ci_env(&[], || {
+        env::testing::with_no_vars(|| {
             assert_eq!(get_ci_provider(), None);
         });
     }
 
     #[test]
     fn github_repository_github_actions() {
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_REPOSITORY", Some("owner/repo")),
             ],
@@ -540,8 +538,8 @@ mod tests {
 
     #[test]
     fn github_repository_buildkite_ssh() {
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("BUILDKITE", Some("true")),
                 ("BUILDKITE_REPO", Some("git@github.com:owner/repo.git")),
             ],
@@ -553,8 +551,8 @@ mod tests {
 
     #[test]
     fn github_repository_buildkite_https() {
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("BUILDKITE", Some("true")),
                 ("BUILDKITE_REPO", Some("https://github.com/owner/repo")),
             ],
@@ -566,8 +564,8 @@ mod tests {
 
     #[test]
     fn github_repository_circleci() {
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("CIRCLECI", Some("true")),
                 (
                     "CIRCLE_REPOSITORY_URL",
@@ -582,8 +580,8 @@ mod tests {
 
     #[test]
     fn github_repository_jenkins() {
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("JENKINS_URL", Some("http://jenkins")),
                 ("GIT_URL", Some("https://github.com/owner/repo.git")),
             ],
@@ -595,15 +593,15 @@ mod tests {
 
     #[test]
     fn github_repository_returns_none_with_no_provider() {
-        with_ci_env(&[("GITHUB_REPOSITORY", Some("owner/repo"))], || {
+        env::testing::with_vars([("GITHUB_REPOSITORY", Some("owner/repo"))], || {
             assert_eq!(get_github_repository(), None);
         });
     }
 
     #[test]
     fn resolve_repository_prefers_flag_over_env() {
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_REPOSITORY", Some("env/env")),
             ],
@@ -619,8 +617,8 @@ mod tests {
         // used — even though this test runs inside a git checkout whose
         // `origin` would otherwise resolve to a different slug. Asserts
         // both the CI fallback and its precedence over the git remote.
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_REPOSITORY", Some("owner/repo")),
             ],
@@ -636,7 +634,7 @@ mod tests {
         // git-remote fallback (`parse_slug`) accepts multi-segment
         // paths that would inject extra request-path segments; an
         // explicit value exercises the same guard deterministically.
-        with_ci_env(&[], || {
+        env::testing::with_no_vars(|| {
             assert!(matches!(
                 resolve_repository(Some("owner/repo/extra")),
                 Err(CliError::Configuration(_))
@@ -652,8 +650,8 @@ mod tests {
 
     #[test]
     fn pull_request_buildkite_reads_env() {
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("BUILDKITE", Some("true")),
                 ("BUILDKITE_PULL_REQUEST", Some("42")),
             ],
@@ -665,8 +663,8 @@ mod tests {
 
     #[test]
     fn pull_request_buildkite_returns_none_when_false() {
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("BUILDKITE", Some("true")),
                 ("BUILDKITE_PULL_REQUEST", Some("false")),
             ],
@@ -678,14 +676,14 @@ mod tests {
 
     #[test]
     fn pull_request_buildkite_returns_none_when_unset() {
-        with_ci_env(&[("BUILDKITE", Some("true"))], || {
+        env::testing::with_vars([("BUILDKITE", Some("true"))], || {
             assert_eq!(get_github_pull_request_number().unwrap(), None);
         });
     }
 
     #[test]
     fn pull_request_returns_none_with_no_provider() {
-        with_ci_env(&[], || {
+        env::testing::with_no_vars(|| {
             assert_eq!(get_github_pull_request_number().unwrap(), None);
         });
     }
@@ -699,8 +697,8 @@ mod tests {
             serde_json::json!({ "pull_request": { "number": 123 } }).to_string(),
         )
         .unwrap();
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_EVENT_PATH", Some(event_path.to_str().unwrap())),
             ],
@@ -714,8 +712,8 @@ mod tests {
     fn pull_request_github_actions_missing_event_file_returns_none() {
         let tmp = tempfile::tempdir().unwrap();
         let missing = tmp.path().join("nope.json");
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_EVENT_PATH", Some(missing.to_str().unwrap())),
             ],
@@ -764,8 +762,8 @@ mod tests {
         );
 
         for event_name in ["pull_request", "pull_request_target"] {
-            with_ci_env(
-                &[
+            env::testing::with_vars(
+                [
                     ("GITHUB_ACTIONS", Some("true")),
                     ("GITHUB_EVENT_NAME", Some(event_name)),
                     ("GITHUB_EVENT_PATH", Some(event_path.to_str().unwrap())),
@@ -793,8 +791,8 @@ mod tests {
         // not.
         let tmp = tempfile::tempdir().unwrap();
         let event_path = write_github_event(tmp.path(), &serde_json::json!({}));
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_EVENT_NAME", Some("push")),
                 ("GITHUB_EVENT_PATH", Some(event_path.to_str().unwrap())),
@@ -811,8 +809,8 @@ mod tests {
 
     #[test]
     fn pull_request_head_sha_uses_buildkite_commit() {
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("BUILDKITE", Some("true")),
                 (
                     "BUILDKITE_COMMIT",
@@ -832,8 +830,8 @@ mod tests {
     fn pull_request_head_sha_drops_a_value_that_is_not_a_revision() {
         // An unset `BUILDKITE_COMMIT` is what `git_refs` reads as the
         // literal `HEAD`; callers must not have to re-check the shape.
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("BUILDKITE", Some("true")),
                 ("BUILDKITE_COMMIT", Some("HEAD")),
             ],
@@ -845,8 +843,8 @@ mod tests {
 
     #[test]
     fn pull_request_head_sha_uses_circle_sha1() {
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("CIRCLECI", Some("true")),
                 (
                     "CIRCLE_SHA1",
@@ -868,8 +866,8 @@ mod tests {
         // plugin builds a pull request merged into its target, which is
         // its default, and nothing distinguishes that from the head-only
         // configuration. No answer beats the wrong one.
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("JENKINS_URL", Some("http://ci")),
                 (
                     "GIT_COMMIT",
@@ -976,8 +974,8 @@ mod tests {
         )
         .unwrap();
 
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_EVENT_NAME", Some("pull_request")),
                 ("GITHUB_EVENT_PATH", Some(event_path.to_str().unwrap())),
@@ -1003,8 +1001,8 @@ mod tests {
         let tmp = tempfile::tempdir().unwrap();
         let event_path = tmp.path().join("event.json");
         std::fs::write(&event_path, serde_json::json!({}).to_string()).unwrap();
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_EVENT_NAME", Some("push")),
                 ("GITHUB_EVENT_PATH", Some(event_path.to_str().unwrap())),
@@ -1021,8 +1019,8 @@ mod tests {
         // Workflows without an event file (e.g. local
         // `act` runs) still set GITHUB_SHA — we must not regress
         // to `None` just because the JSON file isn't there.
-        with_ci_env(
-            &[
+        env::testing::with_vars(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_EVENT_NAME", Some("pull_request")),
                 ("GITHUB_EVENT_PATH", Some("/this/path/does/not/exist")),
diff --git a/crates/mergify-ci/src/git_refs.rs b/crates/mergify-ci/src/git_refs.rs
index 2ca9ab59..24c46ef9 100644
--- a/crates/mergify-ci/src/git_refs.rs
+++ b/crates/mergify-ci/src/git_refs.rs
@@ -27,7 +27,7 @@
 //! `BUILDKITE=true` it invokes `buildkite-agent meta-data set` for
 //! base/head/source.
 
-use std::env;
+use mergify_core::env;
 use std::io::Write;
 use std::process::Command;
 
@@ -152,7 +152,7 @@ pub fn detect(
     output: &mut dyn Output,
     notes_reader: NotesReader<'_>,
 ) -> Result<References, CliError> {
-    if env::var("BUILDKITE").as_deref() == Ok("true")
+    if env::var("BUILDKITE").as_deref() == Some("true")
         && let Some(refs) = detect_from_buildkite(notes_reader)
     {
         return Ok(refs);
@@ -188,16 +188,12 @@ pub fn detect(
 }
 
 fn detect_from_buildkite(notes_reader: NotesReader<'_>) -> Option<References> {
-    let pr = env::var("BUILDKITE_PULL_REQUEST").ok()?;
+    let pr = env::var("BUILDKITE_PULL_REQUEST")?;
     if pr.is_empty() || pr == "false" {
         return None;
     }
-    let commit = env::var("BUILDKITE_COMMIT")
-        .ok()
-        .filter(|s| !s.is_empty())
-        .unwrap_or_else(|| "HEAD".to_string());
-    if let Ok(branch) = env::var("BUILDKITE_BRANCH")
-        && !branch.is_empty()
+    let commit = env::var_non_empty("BUILDKITE_COMMIT").unwrap_or_else(|| "HEAD".to_string());
+    if let Some(branch) = env::var_non_empty("BUILDKITE_BRANCH")
         && let Some(base) = notes_reader(&branch, &commit)
     {
         return Some(References {
@@ -206,9 +202,7 @@ fn detect_from_buildkite(notes_reader: NotesReader<'_>) -> Option<References> {
             source: ReferencesSource::MergeQueue,
         });
     }
-    let base_branch = env::var("BUILDKITE_PULL_REQUEST_BASE_BRANCH")
-        .ok()
-        .filter(|s| !s.is_empty())?;
+    let base_branch = env::var_non_empty("BUILDKITE_PULL_REQUEST_BASE_BRANCH")?;
     Some(References {
         base: Some(base_branch),
         head: commit,
@@ -471,7 +465,7 @@ fn write_github_output(refs: &References) -> Result<(), CliError> {
 }
 
 fn write_buildkite_metadata(refs: &References) -> std::io::Result<()> {
-    if env::var("BUILDKITE").as_deref() != Ok("true") {
+    if env::var("BUILDKITE").as_deref() != Some("true") {
         return Ok(());
     }
     if let Some(base) = refs.base.as_deref() {
@@ -582,10 +576,9 @@ mod tests {
     #[test]
     fn falls_back_to_head_pair_when_no_event() {
         let mut cap = Captured::human();
-        let refs = temp_env::with_vars_unset(
-            ["GITHUB_EVENT_NAME", "GITHUB_EVENT_PATH", "BUILDKITE"],
-            || detect(&mut cap.output, &no_notes).unwrap(),
-        );
+        // An empty overlay is the empty environment: no provider
+        // variable is visible, whatever the host exports.
+        let refs = env::testing::with_no_vars(|| detect(&mut cap.output, &no_notes).unwrap());
         assert_eq!(refs.base.as_deref(), Some("HEAD^"));
         assert_eq!(refs.head, "HEAD");
         assert_eq!(refs.source, ReferencesSource::FallbackLastCommit);
@@ -604,7 +597,7 @@ mod tests {
             }),
         );
         let mut cap = Captured::human();
-        let refs = temp_env::with_vars(
+        let refs = env::testing::with_vars(
             [
                 ("GITHUB_EVENT_NAME", Some("pull_request")),
                 ("GITHUB_EVENT_PATH", Some(path.to_str().unwrap())),
@@ -625,7 +618,7 @@ mod tests {
             &serde_json::json!({"before": "old-sha", "after": "new-sha"}),
         );
         let mut cap = Captured::human();
-        let refs = temp_env::with_vars(
+        let refs = env::testing::with_vars(
             [
                 ("GITHUB_EVENT_NAME", Some("push")),
                 ("GITHUB_EVENT_PATH", Some(path.to_str().unwrap())),
@@ -652,7 +645,7 @@ mod tests {
             }),
         );
         let mut cap = Captured::human();
-        let refs = temp_env::with_vars(
+        let refs = env::testing::with_vars(
             [
                 ("GITHUB_EVENT_NAME", Some("pull_request")),
                 ("GITHUB_EVENT_PATH", Some(path.to_str().unwrap())),
@@ -688,7 +681,7 @@ mod tests {
             }),
         );
         let mut cap = Captured::human();
-        let refs = temp_env::with_vars(
+        let refs = env::testing::with_vars(
             [
                 ("GITHUB_EVENT_NAME", Some("pull_request")),
                 ("GITHUB_EVENT_PATH", Some(path.to_str().unwrap())),
@@ -719,7 +712,7 @@ mod tests {
             }),
         );
         let mut cap = Captured::human();
-        let refs = temp_env::with_vars(
+        let refs = env::testing::with_vars(
             [
                 ("GITHUB_EVENT_NAME", Some("pull_request")),
                 ("GITHUB_EVENT_PATH", Some(path.to_str().unwrap())),
@@ -757,7 +750,7 @@ mod tests {
             }),
         );
         let mut cap = Captured::human();
-        let refs = temp_env::with_vars(
+        let refs = env::testing::with_vars(
             [
                 ("GITHUB_EVENT_NAME", Some("pull_request")),
                 ("GITHUB_EVENT_PATH", Some(path.to_str().unwrap())),
@@ -793,7 +786,7 @@ mod tests {
             }),
         );
         let mut cap = Captured::human();
-        let refs = temp_env::with_vars(
+        let refs = env::testing::with_vars(
             [
                 ("GITHUB_EVENT_NAME", Some("pull_request")),
                 ("GITHUB_EVENT_PATH", Some(path.to_str().unwrap())),
@@ -834,7 +827,7 @@ mod tests {
             }
         };
         let mut cap = Captured::human();
-        let refs = temp_env::with_vars(
+        let refs = env::testing::with_vars(
             [
                 ("GITHUB_EVENT_NAME", Some("pull_request")),
                 ("GITHUB_EVENT_PATH", Some(path.to_str().unwrap())),
@@ -853,7 +846,7 @@ mod tests {
             &serde_json::json!({"pull_request": {"head": {"sha": "h"}}}),
         );
         let mut cap = Captured::human();
-        let err = temp_env::with_vars(
+        let err = env::testing::with_vars(
             [
                 ("GITHUB_EVENT_NAME", Some("pull_request")),
                 ("GITHUB_EVENT_PATH", Some(path.to_str().unwrap())),
@@ -867,7 +860,7 @@ mod tests {
     #[test]
     fn detects_buildkite_pull_request() {
         let mut cap = Captured::human();
-        let refs = temp_env::with_vars(
+        let refs = env::testing::with_vars(
             [
                 ("BUILDKITE", Some("true")),
                 ("BUILDKITE_PULL_REQUEST", Some("42")),
@@ -966,7 +959,7 @@ mod tests {
             head: NOTE_BASE.into(),
             source: ReferencesSource::MergeQueue,
         };
-        temp_env::with_var("GITHUB_OUTPUT", Some(path.to_str().unwrap()), || {
+        env::testing::with_var("GITHUB_OUTPUT", Some(path.to_str().unwrap()), || {
             write_github_output(&refs).unwrap();
         });
         let written = std::fs::read_to_string(&path).unwrap();
diff --git a/crates/mergify-ci/src/github_event.rs b/crates/mergify-ci/src/github_event.rs
index f725225b..4495e9fc 100644
--- a/crates/mergify-ci/src/github_event.rs
+++ b/crates/mergify-ci/src/github_event.rs
@@ -5,7 +5,7 @@
 //! `deny_unknown_fields` on purpose) so the payload's superset of
 //! fields doesn't break us.
 
-use std::env;
+use mergify_core::env;
 use std::path::PathBuf;
 
 use serde::Deserialize;
@@ -65,12 +65,8 @@ pub const PULL_REQUEST_EVENTS: &[&str] = &[
 /// `GitHubEventNotFoundError` being converted to a fallback.
 #[must_use]
 pub fn load() -> Option<(String, GitHubEvent)> {
-    let event_name = env::var("GITHUB_EVENT_NAME")
-        .ok()
-        .filter(|s| !s.is_empty())?;
-    let event_path = env::var("GITHUB_EVENT_PATH")
-        .ok()
-        .filter(|s| !s.is_empty())?;
+    let event_name = env::var_non_empty("GITHUB_EVENT_NAME")?;
+    let event_path = env::var_non_empty("GITHUB_EVENT_PATH")?;
     let path = PathBuf::from(event_path);
     if !path.is_file() {
         return None;
diff --git a/crates/mergify-ci/src/github_output.rs b/crates/mergify-ci/src/github_output.rs
index 001fdeec..9a9f725e 100644
--- a/crates/mergify-ci/src/github_output.rs
+++ b/crates/mergify-ci/src/github_output.rs
@@ -33,7 +33,7 @@
 //! ahead of the `<<`) would let the runner read the block as
 //! something else.
 
-use std::env;
+use mergify_core::env;
 use std::fmt::Write as _;
 use std::fs::OpenOptions;
 use std::io::Write as _;
@@ -45,7 +45,7 @@ use mergify_core::CliError;
 /// output. No-op when the variable is unset or empty — i.e. anywhere
 /// but a GitHub Actions runner.
 pub(crate) fn append(outputs: &[(&'static str, &str)]) -> Result<(), CliError> {
-    let Some(path) = env::var("GITHUB_OUTPUT").ok().filter(|s| !s.is_empty()) else {
+    let Some(path) = env::var_non_empty("GITHUB_OUTPUT") else {
         return Ok(());
     };
     // Assembled first, then written once. Three `writeln!` calls on an
@@ -90,13 +90,13 @@ mod tests {
 
     #[test]
     fn append_is_a_noop_outside_github_actions() {
-        temp_env::with_var("GITHUB_OUTPUT", None::<&str>, || {
+        env::testing::with_var("GITHUB_OUTPUT", None::<&str>, || {
             append(&[("k", "v")]).unwrap();
         });
         // An empty value is treated the same as unset: the runner
         // exports `GITHUB_OUTPUT=` in some contexts, and an empty
         // path is not openable.
-        temp_env::with_var("GITHUB_OUTPUT", Some(""), || {
+        env::testing::with_var("GITHUB_OUTPUT", Some(""), || {
             append(&[("k", "v")]).unwrap();
         });
     }
@@ -105,7 +105,7 @@ mod tests {
     fn append_wraps_every_output_in_its_own_heredoc() {
         let dir = tempfile::tempdir().unwrap();
         let path = dir.path().join("gha_output");
-        temp_env::with_var("GITHUB_OUTPUT", Some(path.to_str().unwrap()), || {
+        env::testing::with_var("GITHUB_OUTPUT", Some(path.to_str().unwrap()), || {
             append(&[("base", "cafef00d"), ("head", "0badc0de")]).unwrap();
         });
         let written = std::fs::read_to_string(&path).unwrap();
@@ -134,7 +134,7 @@ mod tests {
         // step output (MRGFY-8845).
         let dir = tempfile::tempdir().unwrap();
         let path = dir.path().join("gha_output");
-        temp_env::with_var("GITHUB_OUTPUT", Some(path.to_str().unwrap()), || {
+        env::testing::with_var("GITHUB_OUTPUT", Some(path.to_str().unwrap()), || {
             append(&[("base", "cafef00d\nevil=1")]).unwrap();
         });
         let written = std::fs::read_to_string(&path).unwrap();
@@ -152,7 +152,7 @@ mod tests {
         let dir = tempfile::tempdir().unwrap();
         let path = dir.path().join("gha_output");
         std::fs::write(&path, "earlier=1\n").unwrap();
-        temp_env::with_var("GITHUB_OUTPUT", Some(path.to_str().unwrap()), || {
+        env::testing::with_var("GITHUB_OUTPUT", Some(path.to_str().unwrap()), || {
             append(&[("base", "cafef00d")]).unwrap();
         });
         let written = std::fs::read_to_string(&path).unwrap();
diff --git a/crates/mergify-ci/src/junit_process/command.rs b/crates/mergify-ci/src/junit_process/command.rs
index 2f8b96aa..3780b675 100644
--- a/crates/mergify-ci/src/junit_process/command.rs
+++ b/crates/mergify-ci/src/junit_process/command.rs
@@ -25,7 +25,7 @@
 use std::path::{Path, PathBuf};
 
 use mergify_core::auth;
-use mergify_core::env::var_non_empty;
+use mergify_core::env;
 use mergify_core::{CliError, ExitCode, Output};
 
 use crate::detector;
@@ -164,7 +164,7 @@ async fn run_with_cap(
     let metadata = UploadMetadata {
         test_framework: opts.test_framework.map(str::to_string),
         test_language: opts.test_language.map(str::to_string),
-        mergify_test_job_name: var_non_empty("MERGIFY_TEST_JOB_NAME"),
+        mergify_test_job_name: env::var_non_empty("MERGIFY_TEST_JOB_NAME"),
         quarantined: quarantine_result
             .quarantined
             .iter()
@@ -337,7 +337,7 @@ fn resolve_test_exit_code(explicit: Option<i32>) -> Result<Option<i32>, CliError
     if explicit.is_some() {
         return Ok(explicit);
     }
-    let Some(raw) = var_non_empty("MERGIFY_TEST_EXIT_CODE") else {
+    let Some(raw) = env::var_non_empty("MERGIFY_TEST_EXIT_CODE") else {
         return Ok(None);
     };
     raw.parse::<i32>().map(Some).map_err(|e| {
@@ -606,10 +606,7 @@ fn upload_status_label(
 /// on stderr instead of erroring.
 fn maybe_write_github_output(status: &str) {
     use std::io::Write as _;
-    let Some(path) = std::env::var("GITHUB_OUTPUT")
-        .ok()
-        .filter(|s| !s.is_empty())
-    else {
+    let Some(path) = env::var_non_empty("GITHUB_OUTPUT") else {
         return;
     };
     let result = std::fs::OpenOptions::new()
@@ -634,7 +631,7 @@ fn maybe_write_github_output(status: &str) {
 /// they're permanent misconfiguration; transient failures (5xx,
 /// 408, 429, network) as warnings.
 fn gha_upload_annotation(error: &upload::UploadError) -> Option<String> {
-    if std::env::var("GITHUB_ACTIONS").as_deref() != Ok("true") {
+    if env::var("GITHUB_ACTIONS").as_deref() != Some("true") {
         return None;
     }
     Some(if error.is_rejection() {
@@ -659,7 +656,7 @@ fn gha_upload_annotation(error: &upload::UploadError) -> Option<String> {
 /// summary / checks UI — otherwise it only appears in the human
 /// report prose. Never an error: the CI outcome is unaffected.
 fn gha_oversized_annotation(names: &[String]) -> Option<String> {
-    if std::env::var("GITHUB_ACTIONS").as_deref() != Ok("true") {
+    if env::var("GITHUB_ACTIONS").as_deref() != Some("true") {
         return None;
     }
     Some(format!(
@@ -890,7 +887,7 @@ mod tests {
         // `gha-mergify-ci` action uses when no runner exit code is
         // available. Pin so a future refactor can't accidentally
         // invert the precedence.
-        let got = temp_env::with_var("MERGIFY_TEST_EXIT_CODE", Some("42"), || {
+        let got = env::testing::with_var("MERGIFY_TEST_EXIT_CODE", Some("42"), || {
             resolve_test_exit_code(Some(0)).unwrap()
         });
         assert_eq!(got, Some(0));
@@ -909,7 +906,7 @@ mod tests {
         // fix drops the clap `env` hook and routes the env var
         // through here — empty must collapse to `None`, the
         // same shape no env var would produce.
-        let got = temp_env::with_var("MERGIFY_TEST_EXIT_CODE", Some(""), || {
+        let got = env::testing::with_var("MERGIFY_TEST_EXIT_CODE", Some(""), || {
             resolve_test_exit_code(None).unwrap()
         });
         assert_eq!(got, None);
@@ -917,7 +914,7 @@ mod tests {
 
     #[test]
     fn resolve_test_exit_code_parses_non_empty_env_var() {
-        let got = temp_env::with_var("MERGIFY_TEST_EXIT_CODE", Some("7"), || {
+        let got = env::testing::with_var("MERGIFY_TEST_EXIT_CODE", Some("7"), || {
             resolve_test_exit_code(None).unwrap()
         });
         assert_eq!(got, Some(7));
@@ -929,7 +926,7 @@ mod tests {
         // real misconfiguration, not a "no value" sentinel —
         // error loudly with the offending value in the message so
         // the user can spot the typo without having to dig.
-        let err = temp_env::with_var("MERGIFY_TEST_EXIT_CODE", Some("not-an-int"), || {
+        let err = env::testing::with_var("MERGIFY_TEST_EXIT_CODE", Some("not-an-int"), || {
             resolve_test_exit_code(None).unwrap_err()
         });
         let msg = err.to_string();
@@ -1098,13 +1095,13 @@ mod tests {
     #[test]
     fn gha_oversized_annotation_lists_names_only_on_gha() {
         // Outside GitHub Actions: no annotation.
-        let none = temp_env::with_var("GITHUB_ACTIONS", None::<&str>, || {
+        let none = env::testing::with_var("GITHUB_ACTIONS", None::<&str>, || {
             gha_oversized_annotation(&["a.big".to_string()])
         });
         assert!(none.is_none());
         // On GitHub Actions: a warning naming the dropped tests, never
         // an error (CI outcome is unaffected).
-        let ann = temp_env::with_var("GITHUB_ACTIONS", Some("true"), || {
+        let ann = env::testing::with_var("GITHUB_ACTIONS", Some("true"), || {
             gha_oversized_annotation(&["a.big".to_string(), "b.huge".to_string()])
         })
         .unwrap();
@@ -1134,7 +1131,7 @@ mod tests {
         write_oversized_cases(&mut report, std::slice::from_ref(&long));
         assert!(!report.contains(&long), "the report printed the whole name");
 
-        let ann = temp_env::with_var("GITHUB_ACTIONS", Some("true"), || {
+        let ann = env::testing::with_var("GITHUB_ACTIONS", Some("true"), || {
             gha_oversized_annotation(std::slice::from_ref(&long))
         })
         .unwrap();
@@ -1161,7 +1158,6 @@ mod tests {
     // banner text drifting).
     mod orchestrator {
         use super::*;
-        use crate::testing::with_ci_env_async;
         use mergify_core::{OutputMode, StdioOutput};
         use std::sync::{Arc, Mutex};
         use wiremock::matchers::{method, path};
@@ -1240,7 +1236,7 @@ mod tests {
 
             let api_url = server.uri();
             let mut cap = captured();
-            let code = with_ci_env_async(&[], async {
+            let code = env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some(&api_url),
                     token: Some("secret"),
@@ -1281,7 +1277,7 @@ mod tests {
             let api_url = server.uri();
             let mut cap = captured();
             let cap_bytes = 4 * 1024;
-            let code = with_ci_env_async(&[], async {
+            let code = env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some(&api_url),
                     token: Some("secret"),
@@ -1422,8 +1418,8 @@ mod tests {
             // checks survive stamping. With the environment scrubbed
             // it would only ever emit `test.run.id`, and the check
             // would pass on an empty resource.
-            with_ci_env_async(
-                &[
+            env::testing::with_vars_async(
+                [
                     ("GITHUB_ACTIONS", Some("true")),
                     ("GITHUB_REPOSITORY", Some("owner/repo")),
                     (
@@ -1525,7 +1521,7 @@ mod tests {
             let file = write_xml(&tmp, "report.xml", &incompressible_failures_xml(30, 2048));
             let api_url = server.uri();
             let mut cap = captured();
-            with_ci_env_async(&[], async {
+            env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some(&api_url),
                     token: Some("secret"),
@@ -1566,7 +1562,7 @@ mod tests {
 
             let api_url = server.uri();
             let mut cap = captured();
-            with_ci_env_async(&[], async {
+            env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some(&api_url),
                     token: Some("secret"),
@@ -1604,7 +1600,7 @@ mod tests {
 
             let api_url = server.uri();
             let mut cap = captured();
-            with_ci_env_async(&[], async {
+            env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some(&api_url),
                     token: Some("secret"),
@@ -1640,7 +1636,7 @@ mod tests {
 
             let api_url = server.uri();
             let mut cap = captured();
-            with_ci_env_async(&[], async {
+            env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some(&api_url),
                     token: Some("secret"),
@@ -1732,7 +1728,7 @@ mod tests {
 
             let api_url = server.uri();
             let mut cap = captured();
-            with_ci_env_async(&[], async {
+            env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some(&api_url),
                     token: Some("secret"),
@@ -1761,7 +1757,7 @@ mod tests {
 
             let api_url = server.uri();
             let mut cap = captured();
-            with_ci_env_async(&[], async {
+            env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some(&api_url),
                     token: Some("secret"),
@@ -1829,8 +1825,8 @@ mod tests {
             let output_path = github_output.to_string_lossy().into_owned();
             let mut cap = captured();
             // 64-byte cap: smaller than any single case's gzipped span.
-            let code = with_ci_env_async(
-                &[
+            let code = env::testing::with_vars_async(
+                [
                     ("GITHUB_ACTIONS", Some("true")),
                     ("GITHUB_OUTPUT", Some(&output_path)),
                 ],
@@ -1872,7 +1868,7 @@ mod tests {
 
             let api_url = server.uri();
             let mut cap = captured();
-            let code = with_ci_env_async(&[], async {
+            let code = env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some(&api_url),
                     token: Some("secret"),
@@ -1908,7 +1904,7 @@ mod tests {
 
             let api_url = server.uri();
             let mut cap = captured();
-            let code = with_ci_env_async(&[], async {
+            let code = env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some(&api_url),
                     token: Some("secret"),
@@ -1952,7 +1948,7 @@ mod tests {
 
             let api_url = server.uri();
             let mut cap = captured();
-            let code = with_ci_env_async(&[], async {
+            let code = env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some(&api_url),
                     token: Some("secret"),
@@ -2011,8 +2007,8 @@ mod tests {
         ) -> (ExitCode, String) {
             let mut cap = captured();
             let output_path = github_output.to_string_lossy().into_owned();
-            let code = with_ci_env_async(
-                &[
+            let code = env::testing::with_vars_async(
+                [
                     ("GITHUB_ACTIONS", Some("true")),
                     ("GITHUB_OUTPUT", Some(&output_path)),
                 ],
@@ -2131,7 +2127,7 @@ mod tests {
 
             let api_url = server.uri();
             let mut cap = captured();
-            let code = with_ci_env_async(&[], async {
+            let code = env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some(&api_url),
                     token: Some("secret"),
@@ -2179,7 +2175,7 @@ mod tests {
             // No mock server: if the orchestrator skips the early
             // exit and tries to reach the API, the bogus URL will
             // fail the test loudly.
-            let code = with_ci_env_async(&[], async {
+            let code = env::testing::with_no_vars_async(async {
                 let opts = JunitProcessOptions {
                     api_url: Some("http://127.0.0.1:1"),
                     token: Some("secret"),
diff --git a/crates/mergify-ci/src/junit_process/spans.rs b/crates/mergify-ci/src/junit_process/spans.rs
index ae988ec2..4d863bea 100644
--- a/crates/mergify-ci/src/junit_process/spans.rs
+++ b/crates/mergify-ci/src/junit_process/spans.rs
@@ -446,9 +446,10 @@ impl RandomBytes for OsRandom {
 
 #[cfg(test)]
 mod tests {
+    use mergify_core::env;
+
     use super::*;
     use crate::junit_process::junit::Failure;
-    use crate::testing::with_ci_env;
 
     /// Deterministic byte source for tests. Bytes are consumed
     /// in order. Tests provide enough buffer for the spans they
@@ -538,7 +539,8 @@ mod tests {
 
         let now: u64 = 1_700_000_000_000_000_000;
         let metadata = UploadMetadata::default();
-        let built = with_ci_env(&[], || build_traces_with(&parsed, &metadata, now, &mut rng));
+        let built =
+            env::testing::with_no_vars(|| build_traces_with(&parsed, &metadata, now, &mut rng));
 
         assert_eq!(built.oversized_case_names, vec![oversized.clone()]);
 
@@ -589,7 +591,7 @@ mod tests {
         bytes.extend(std::iter::repeat_n(0x55, 8));
         let mut rng = FixedRng::new(bytes);
 
-        let built = with_ci_env(&[], || {
+        let built = env::testing::with_no_vars(|| {
             build_traces_with(
                 &parsed,
                 &UploadMetadata::default(),
@@ -618,7 +620,7 @@ mod tests {
 
         let now: u64 = 1_700_000_000_000_000_000;
         let metadata = UploadMetadata::default();
-        let built = with_ci_env(&[], || {
+        let built = env::testing::with_no_vars(|| {
             build_traces_with(&sample_parsed(), &metadata, now, &mut rng)
         });
 
@@ -661,7 +663,7 @@ mod tests {
         let mut rng = FixedRng::new(vec![0xFF; 256]);
         let now: u64 = 1_700_000_000_000_000_000;
         let metadata = UploadMetadata::default();
-        let built = with_ci_env(&[], || {
+        let built = env::testing::with_no_vars(|| {
             build_traces_with(&sample_parsed(), &metadata, now, &mut rng)
         });
         let spans = &built.request.resource_spans[0].scope_spans[0].spans;
@@ -696,7 +698,7 @@ mod tests {
     fn case_attributes_include_file_line_and_code_function() {
         let mut rng = FixedRng::new(vec![0xFF; 256]);
         let metadata = UploadMetadata::default();
-        let built = with_ci_env(&[], || {
+        let built = env::testing::with_no_vars(|| {
             build_traces_with(&sample_parsed(), &metadata, 0, &mut rng)
         });
         let spans = &built.request.resource_spans[0].scope_spans[0].spans;
@@ -737,8 +739,8 @@ mod tests {
     fn resource_attributes_carry_ci_env_when_set() {
         let mut rng = FixedRng::new(vec![0xFF; 256]);
         let metadata = UploadMetadata::default();
-        let built = with_ci_env(
-            &[
+        let built = env::testing::with_vars(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_REPOSITORY", Some("owner/repo")),
                 ("GITHUB_WORKFLOW", Some("CI")),
@@ -795,7 +797,7 @@ mod tests {
             mergify_test_job_name: None,
             quarantined: BTreeSet::new(),
         };
-        let built = with_ci_env(&[], || {
+        let built = env::testing::with_no_vars(|| {
             build_traces_with(&sample_parsed(), &metadata, 0, &mut rng)
         });
         let spans = &built.request.resource_spans[0].scope_spans[0].spans;
@@ -822,7 +824,7 @@ mod tests {
         let mut rng = FixedRng::new(vec![0xFF; 256]);
         let now: u64 = 1_000_000_000_000_000_000;
         let metadata = UploadMetadata::default();
-        let built = with_ci_env(&[], || {
+        let built = env::testing::with_no_vars(|| {
             build_traces_with(&sample_parsed(), &metadata, now, &mut rng)
         });
         let spans = &built.request.resource_spans[0].scope_spans[0].spans;
diff --git a/crates/mergify-ci/src/junit_process/split.rs b/crates/mergify-ci/src/junit_process/split.rs
index 54d8442d..bfc8170a 100644
--- a/crates/mergify-ci/src/junit_process/split.rs
+++ b/crates/mergify-ci/src/junit_process/split.rs
@@ -555,7 +555,8 @@ mod tests {
     use super::*;
     use crate::junit_process::junit::{Failure, ParseResult, TestCase, TestStatus};
     use crate::junit_process::spans::{UploadMetadata, build_traces};
-    use crate::testing::{incompressible, with_ci_env};
+    use crate::testing::incompressible;
+    use mergify_core::env;
     use std::collections::BTreeSet;
     use std::time::Duration;
 
@@ -595,7 +596,7 @@ mod tests {
             mergify_test_job_name: None,
             quarantined: BTreeSet::new(),
         };
-        with_ci_env(&[], || build_traces(&parsed, &metadata)).request
+        env::testing::with_no_vars(|| build_traces(&parsed, &metadata)).request
     }
 
     /// Collect the `test.case.name` of every case span in a chunk.
diff --git a/crates/mergify-ci/src/queue_info.rs b/crates/mergify-ci/src/queue_info.rs
index d2db01e2..7c2b845a 100644
--- a/crates/mergify-ci/src/queue_info.rs
+++ b/crates/mergify-ci/src/queue_info.rs
@@ -109,6 +109,7 @@ fn write_github_output(metadata: &Value) -> Result<(), CliError> {
 #[cfg(test)]
 mod tests {
     use mergify_core::ExitCode;
+    use mergify_core::env;
     use mergify_test_support::Captured;
     use serde_json::json;
 
@@ -141,7 +142,7 @@ mod tests {
     fn prints_whole_note_payload() {
         let note = || Some(sample());
         let mut cap = Captured::human();
-        temp_env::with_var("GITHUB_OUTPUT", None::<&str>, || {
+        env::testing::with_var("GITHUB_OUTPUT", None::<&str>, || {
             run_with_reader(&mut cap.output, &note).unwrap();
         });
         let stdout = cap.stdout();
@@ -161,7 +162,7 @@ mod tests {
         let gha_output = dir.path().join("gha_output");
         let note = || Some(sample());
         let mut cap = Captured::human();
-        temp_env::with_var("GITHUB_OUTPUT", Some(gha_output.to_str().unwrap()), || {
+        env::testing::with_var("GITHUB_OUTPUT", Some(gha_output.to_str().unwrap()), || {
             run_with_reader(&mut cap.output, &note).unwrap();
         });
         let written = std::fs::read_to_string(&gha_output).unwrap();
diff --git a/crates/mergify-ci/src/scopes_detect/mod.rs b/crates/mergify-ci/src/scopes_detect/mod.rs
index b313e346..b85e34f3 100644
--- a/crates/mergify-ci/src/scopes_detect/mod.rs
+++ b/crates/mergify-ci/src/scopes_detect/mod.rs
@@ -25,14 +25,13 @@ pub mod config;
 pub mod matching;
 pub mod outputs;
 
-use std::env;
 use std::io::Write;
 use std::path::Path;
 use std::path::PathBuf;
 
 use mergify_core::CliError;
 use mergify_core::Output;
-use mergify_core::env::var_non_empty;
+use mergify_core::env;
 use serde::Serialize;
 
 use crate::git_refs;
@@ -128,7 +127,7 @@ fn resolve_config_path(explicit: Option<&Path>) -> Result<PathBuf, CliError> {
             path.display(),
         )));
     }
-    if let Some(env_path) = var_non_empty("MERGIFY_CONFIG_PATH") {
+    if let Some(env_path) = env::var_non_empty("MERGIFY_CONFIG_PATH") {
         let p = PathBuf::from(&env_path);
         if !p.is_file() {
             return Err(CliError::Configuration(format!(
@@ -240,7 +239,7 @@ fn emit_scopes_listing(
     by_scope: &std::collections::BTreeMap<String, Vec<String>>,
     output: &mut dyn Output,
 ) -> Result<(), CliError> {
-    let actions_debug = env::var("ACTIONS_STEP_DEBUG").as_deref() == Ok("true");
+    let actions_debug = env::var("ACTIONS_STEP_DEBUG").as_deref() == Some("true");
     if hit.is_empty() {
         output.status("No scopes matched.")?;
         return Ok(());
@@ -289,7 +288,6 @@ fn write_detected_scopes(
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::testing::with_ci_env;
     use mergify_test_support::Captured;
 
     #[test]
@@ -330,7 +328,7 @@ mod tests {
         // so this function owns the lookup — and the empty branch
         // here must fall through to autodetect rather than report
         // a malformed env var.
-        let result = temp_env::with_var("MERGIFY_CONFIG_PATH", Some(""), || {
+        let result = env::testing::with_var("MERGIFY_CONFIG_PATH", Some(""), || {
             resolve_config_path(None)
         });
         // Either autodetect found a real config (cargo test runs
@@ -354,9 +352,10 @@ mod tests {
         // value that doesn't exist, the error must name the env
         // var + the bogus path so the user can spot the typo
         // without having to dig.
-        let err = temp_env::with_var("MERGIFY_CONFIG_PATH", Some("/no/such/.mergify.yml"), || {
-            resolve_config_path(None).unwrap_err()
-        });
+        let err =
+            env::testing::with_var("MERGIFY_CONFIG_PATH", Some("/no/such/.mergify.yml"), || {
+                resolve_config_path(None).unwrap_err()
+            });
         let msg = err.to_string();
         assert!(msg.contains("MERGIFY_CONFIG_PATH="), "got: {msg}");
         assert!(msg.contains("/no/such/.mergify.yml"), "got: {msg}");
@@ -402,11 +401,10 @@ mod tests {
         // "select all scopes" branch and reports every
         // configured scope as touched. No git operations.
         //
-        // The `with_ci_env` wrapper scrubs `GITHUB_OUTPUT` so a
-        // GHA runner executing the suite doesn't see `run()`
-        // append a heredoc to its real step-output file (which
-        // would break the runner step with "Matching delimiter
-        // not found").
+        // The empty overlay hides `GITHUB_OUTPUT` so a GHA runner
+        // executing the suite doesn't see `run()` append a heredoc
+        // to its real step-output file (which would break the
+        // runner step with "Matching delimiter not found").
         let tmp = tempfile::tempdir().unwrap();
         let cfg = tmp.path().join("mergify.yml");
         std::fs::write(
@@ -415,7 +413,7 @@ mod tests {
         )
         .unwrap();
         let mut cap = Captured::human();
-        with_ci_env(&[], || {
+        env::testing::with_no_vars(|| {
             run(
                 ScopesOptions {
                     config: Some(&cfg),
@@ -444,7 +442,7 @@ mod tests {
         let cfg = tmp.path().join("mergify.yml");
         std::fs::write(&cfg, "scopes:\n  source:\n    manual: null\n").unwrap();
         let mut cap = Captured::human();
-        let err = with_ci_env(&[], || {
+        let err = env::testing::with_no_vars(|| {
             run(
                 ScopesOptions {
                     config: Some(&cfg),
@@ -475,7 +473,7 @@ mod tests {
         .unwrap();
         let out = tmp.path().join("detected.json");
         let mut cap = Captured::human();
-        with_ci_env(&[], || {
+        env::testing::with_no_vars(|| {
             run(
                 ScopesOptions {
                     config: Some(&cfg),
diff --git a/crates/mergify-ci/src/scopes_detect/outputs.rs b/crates/mergify-ci/src/scopes_detect/outputs.rs
index d3582beb..da3bacd4 100644
--- a/crates/mergify-ci/src/scopes_detect/outputs.rs
+++ b/crates/mergify-ci/src/scopes_detect/outputs.rs
@@ -5,8 +5,8 @@
 //! `mergify_cli/ci/scopes/cli.py` and stay quiet when their
 //! respective environment knob is absent.
 
+use mergify_core::env;
 use std::collections::BTreeSet;
-use std::env;
 use std::fmt::Write as _;
 use std::fs::OpenOptions;
 use std::io::Write;
@@ -64,7 +64,7 @@ pub fn maybe_write_buildkite_metadata(
     all: &BTreeSet<String>,
     hit: &BTreeSet<String>,
 ) -> Result<(), CliError> {
-    if env::var("BUILDKITE").as_deref() != Ok("true") {
+    if env::var("BUILDKITE").as_deref() != Some("true") {
         return Ok(());
     }
     let payload = scopes_dict_json(all, hit);
@@ -114,10 +114,7 @@ pub fn maybe_write_github_step_summary(
     all: &BTreeSet<String>,
     hit: &BTreeSet<String>,
 ) -> Result<(), CliError> {
-    let Some(path) = env::var("GITHUB_STEP_SUMMARY")
-        .ok()
-        .filter(|s| !s.is_empty())
-    else {
+    let Some(path) = env::var_non_empty("GITHUB_STEP_SUMMARY") else {
         return Ok(());
     };
     let md = build_summary_markdown(refs, all, hit);
@@ -138,7 +135,7 @@ pub fn maybe_write_buildkite_annotation(
     all: &BTreeSet<String>,
     hit: &BTreeSet<String>,
 ) {
-    if env::var("BUILDKITE").as_deref() != Ok("true") {
+    if env::var("BUILDKITE").as_deref() != Some("true") {
         return;
     }
     let md = build_summary_markdown(refs, all, hit);
diff --git a/crates/mergify-ci/src/scopes_send.rs b/crates/mergify-ci/src/scopes_send.rs
index 06a1a265..5fba0e37 100644
--- a/crates/mergify-ci/src/scopes_send.rs
+++ b/crates/mergify-ci/src/scopes_send.rs
@@ -228,6 +228,7 @@ struct SendScopesRequest<'a> {
 mod tests {
     use std::fs;
 
+    use mergify_core::env;
     use mergify_test_support::Captured;
     use wiremock::Mock;
     use wiremock::MockServer;
@@ -238,13 +239,11 @@ mod tests {
     use wiremock::matchers::path;
 
     use super::*;
-    use crate::testing::with_ci_env;
-    use crate::testing::with_ci_env_async;
     use crate::testing::write_github_event;
 
     #[test]
     fn resolve_pull_request_prefers_explicit() {
-        with_ci_env(&[], || {
+        env::testing::with_no_vars(|| {
             assert_eq!(resolve_pull_request(Some(7)).unwrap(), Some(7));
         });
     }
@@ -287,7 +286,7 @@ mod tests {
     #[tokio::test]
     async fn run_skips_when_no_pull_request_detected() {
         let mut cap = Captured::human();
-        with_ci_env_async(&[("GITHUB_REPOSITORY", Some("owner/repo"))], async {
+        env::testing::with_vars_async([("GITHUB_REPOSITORY", Some("owner/repo"))], async {
             run(
                 ScopesSendOptions {
                     repository: None,
@@ -331,8 +330,8 @@ mod tests {
         let api_url = server.uri();
         let direct = vec!["a".to_string()];
 
-        with_ci_env_async(
-            &[
+        env::testing::with_vars_async(
+            [
                 ("BUILDKITE", Some("true")),
                 ("BUILDKITE_REPO", Some("git@github.com:owner/repo.git")),
                 ("BUILDKITE_PULL_REQUEST", Some("99")),
@@ -554,8 +553,8 @@ mod tests {
         let api_url = server.uri();
         let direct = vec!["a".to_string()];
 
-        with_ci_env_async(
-            &[
+        env::testing::with_vars_async(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_EVENT_NAME", Some("pull_request")),
                 ("GITHUB_EVENT_PATH", Some(event_path.to_str().unwrap())),
@@ -620,8 +619,8 @@ mod tests {
         let api_url = server.uri();
         let direct = vec!["backend".to_string()];
 
-        with_ci_env_async(
-            &[
+        env::testing::with_vars_async(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_EVENT_NAME", Some("pull_request")),
                 ("GITHUB_EVENT_PATH", Some(event_path.to_str().unwrap())),
diff --git a/crates/mergify-ci/src/testing.rs b/crates/mergify-ci/src/testing.rs
index db729e76..1a496126 100644
--- a/crates/mergify-ci/src/testing.rs
+++ b/crates/mergify-ci/src/testing.rs
@@ -1,130 +1,9 @@
 //! Test-only helpers shared across the CI-aware command modules
 //! (`detector`, `scopes_send`, `tests_show`, `tests_quarantine`).
-//!
-//! These modules test CI-provider-aware code paths and need to scrub
-//! the host's CI env vars before running each case — otherwise a
-//! test running on a real Buildkite/Actions/Circle/Jenkins host
-//! inherits provider state and the detector picks the wrong branch.
-//! Two flavors: a sync `with_ci_env` and an async `with_ci_env_async`
-//! (used by the `#[tokio::test]` cases).
 
-use std::future::Future;
 use std::path::Path;
 use std::path::PathBuf;
 
-/// Env vars the CI-provider detection chain inspects. Clear every
-/// one of them before applying the test-specific overrides, so the
-/// host environment can't leak into the test — running the test
-/// suite *on* a real GitHub Actions / `CircleCI` / Jenkins / Buildkite
-/// host would otherwise produce `vcs.ref.head.name` etc. values
-/// taken from the runner instead of the test's explicit override
-/// and silently fail.
-///
-/// `GITHUB_OUTPUT` belongs on this list too — when the suite runs
-/// on a GHA runner that var points at the runner's real
-/// step-output file, and any test that exercises a code path
-/// appending a heredoc (e.g. `ci scopes` →
-/// `MERGIFY_SCOPES<<ghadelimiter_…`) will splice its own
-/// delimiter into the runner's file. GHA then fails the step with
-/// "Matching delimiter not found". Scrubbing it forces the no-op
-/// `env::var("GITHUB_OUTPUT").ok()` branch unless the test
-/// explicitly points it at a temp file.
-///
-/// Keep this list aligned with every `env::var(...)` call across
-/// `detector::*`; new detector helpers must add their inputs here
-/// or their tests will be flaky on CI.
-const CI_ENV_VARS: &[&str] = &[
-    // Provider selection.
-    "JENKINS_URL",
-    "GITHUB_ACTIONS",
-    "CIRCLECI",
-    "BUILDKITE",
-    // Repository identity (cross-provider).
-    "GITHUB_REPOSITORY",
-    "GITHUB_EVENT_PATH",
-    "GITHUB_OUTPUT",
-    "CIRCLE_REPOSITORY_URL",
-    "BUILDKITE_REPO",
-    "BUILDKITE_PULL_REQUEST",
-    "GIT_URL",
-    // GitHub Actions resource attributes.
-    "GITHUB_EVENT_NAME",
-    "GITHUB_HEAD_REF",
-    "GITHUB_REF_NAME",
-    "GITHUB_BASE_REF",
-    "GITHUB_WORKFLOW",
-    "GITHUB_JOB",
-    "GITHUB_RUN_ID",
-    "GITHUB_RUN_ATTEMPT",
-    "GITHUB_SHA",
-    "RUNNER_NAME",
-    // CircleCI resource attributes.
-    "CIRCLE_BRANCH",
-    "CIRCLE_JOB",
-    "CIRCLE_WORKFLOW_ID",
-    "CIRCLE_BUILD_NUM",
-    "CIRCLE_SHA1",
-    "CIRCLE_PULL_REQUESTS",
-    // Jenkins resource attributes.
-    "JOB_NAME",
-    "GIT_BRANCH",
-    "GIT_COMMIT",
-    "CHANGE_TARGET",
-    "NODE_NAME",
-    "BUILD_ID",
-    // Buildkite resource attributes.
-    "BUILDKITE_PIPELINE_SLUG",
-    "BUILDKITE_LABEL",
-    "BUILDKITE_STEP_KEY",
-    "BUILDKITE_BRANCH",
-    "BUILDKITE_PULL_REQUEST_BASE_BRANCH",
-    "BUILDKITE_AGENT_NAME",
-    "BUILDKITE_BUILD_ID",
-    "BUILDKITE_BUILD_URL",
-    "BUILDKITE_RETRY_COUNT",
-    "BUILDKITE_COMMIT",
-    // CLI-side metadata that the upload layer reads into resource
-    // attributes; explicitly scrubbed so tests that don't set it
-    // get a deterministic `mergify.test.job.name` (absent).
-    "MERGIFY_TEST_JOB_NAME",
-    // Consumed by `junit_process::command::resolve_test_exit_code`
-    // (silent-failure detection). Scrub so the orchestrator tests
-    // don't pick up a developer's local export or a CI host that
-    // happens to set it, which would change which verdict branch
-    // the assertions land in.
-    "MERGIFY_TEST_EXIT_CODE",
-];
-
-fn merged_overrides(extra: &[(&str, Option<&str>)]) -> Vec<(String, Option<String>)> {
-    let mut vars: Vec<(String, Option<String>)> = CI_ENV_VARS
-        .iter()
-        .map(|k| ((*k).to_string(), None))
-        .collect();
-    for (k, v) in extra {
-        vars.push(((*k).to_string(), v.map(ToString::to_string)));
-    }
-    vars
-}
-
-/// Run `f` with the CI-provider env vars cleared, plus the
-/// `extra` overrides applied on top.
-pub(crate) fn with_ci_env<F, R>(extra: &[(&str, Option<&str>)], f: F) -> R
-where
-    F: FnOnce() -> R,
-{
-    temp_env::with_vars(merged_overrides(extra), f)
-}
-
-/// Async counterpart to [`with_ci_env`]. Used by `#[tokio::test]`
-/// cases in `scopes_send` — the sync variant can't bridge `.await`
-/// points.
-pub(crate) async fn with_ci_env_async<F, R>(extra: &[(&str, Option<&str>)], f: F) -> R
-where
-    F: Future<Output = R>,
-{
-    temp_env::async_with_vars(merged_overrides(extra), f).await
-}
-
 /// Write `payload` as a GitHub Actions event file under `dir` and
 /// return its path, ready to point `GITHUB_EVENT_PATH` at. The
 /// payload-reading helpers across `detector` and `scopes_send` all
diff --git a/crates/mergify-ci/src/tests_quarantine.rs b/crates/mergify-ci/src/tests_quarantine.rs
index df934ce5..fd85ee1b 100644
--- a/crates/mergify-ci/src/tests_quarantine.rs
+++ b/crates/mergify-ci/src/tests_quarantine.rs
@@ -401,6 +401,7 @@ mod tests {
 
     use mergify_core::OutputMode;
     use mergify_core::StdioOutput;
+    use mergify_core::env;
     use serde_json::json;
     use wiremock::Mock;
     use wiremock::MockServer;
@@ -410,7 +411,6 @@ mod tests {
     use wiremock::matchers::path as path_matcher;
 
     use super::*;
-    use crate::testing::with_ci_env_async;
 
     type SharedBytes = Arc<Mutex<Vec<u8>>>;
 
@@ -805,8 +805,8 @@ mod tests {
         // With no `--repository`, the command resolves the repository
         // from the CI environment — here GitHub Actions'
         // `GITHUB_REPOSITORY` — and queries that repository's endpoint.
-        with_ci_env_async(
-            &[
+        env::testing::with_vars_async(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_REPOSITORY", Some("owner/repo")),
             ],
diff --git a/crates/mergify-ci/src/tests_show.rs b/crates/mergify-ci/src/tests_show.rs
index 227dfbe0..ad049a49 100644
--- a/crates/mergify-ci/src/tests_show.rs
+++ b/crates/mergify-ci/src/tests_show.rs
@@ -370,6 +370,7 @@ mod tests {
 
     use mergify_core::OutputMode;
     use mergify_core::StdioOutput;
+    use mergify_core::env;
     use serde_json::json;
     use wiremock::Mock;
     use wiremock::MockServer;
@@ -378,7 +379,6 @@ mod tests {
     use wiremock::matchers::path as path_matcher;
 
     use super::*;
-    use crate::testing::with_ci_env_async;
 
     type SharedBytes = Arc<Mutex<Vec<u8>>>;
 
@@ -522,8 +522,8 @@ mod tests {
         // With no `--repository`, the command resolves the repository
         // from the CI environment — here GitHub Actions'
         // `GITHUB_REPOSITORY` — and queries that repository's endpoint.
-        with_ci_env_async(
-            &[
+        env::testing::with_vars_async(
+            [
                 ("GITHUB_ACTIONS", Some("true")),
                 ("GITHUB_REPOSITORY", Some("owner/repo")),
             ],