From 06c5f7d7506bd70f58cf781949947ad4c03f1927 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Fri, 18 Sep 2026 17:39:44 +0200
Subject: [PATCH 1/2] add custom test runner test

---
 tests/pretty/custom-test-runner.pp | 33 ++++++++++++++++++++++++++++++
 tests/pretty/custom-test-runner.rs | 25 ++++++++++++++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 tests/pretty/custom-test-runner.pp
 create mode 100644 tests/pretty/custom-test-runner.rs

diff --git a/tests/pretty/custom-test-runner.pp b/tests/pretty/custom-test-runner.pp
new file mode 100644
index 0000000000000..dc777e37e3041
--- /dev/null
+++ b/tests/pretty/custom-test-runner.pp
@@ -0,0 +1,33 @@
+#![feature(prelude_import)]
+#![no_std]
+//@ compile-flags: --crate-type=lib --test --remap-path-prefix={{src-base}}/=/the/src/ --remap-path-prefix={{src-base}}\=/the/src/
+//@ pretty-compare-only
+//@ pretty-mode:expanded
+//@ pp-exact:custom-test-runner.pp
+
+// Example taken from the unstable book.
+
+#![feature(custom_test_frameworks)]
+#![test_runner(my_runner)]
+extern crate std;
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+
+fn my_runner(tests: &[&i32]) {
+    for t in tests {
+        if **t == 0 {
+
+
+            { ::std::io::_print(format_args!("PASSED\n")); };
+        } else { { ::std::io::_print(format_args!("FAILED\n")); }; }
+    }
+}
+#[rustc_test_marker = "WILL_PASS"]
+pub const WILL_PASS: i32 = 0;
+#[rustc_test_marker = "WILL_FAIL"]
+pub const WILL_FAIL: i32 = 4;
+extern crate test;
+#[rustc_main]
+#[coverage(off)]
+#[doc(hidden)]
+pub fn main() -> () { my_runner(&[&WILL_FAIL, &WILL_PASS]) }
diff --git a/tests/pretty/custom-test-runner.rs b/tests/pretty/custom-test-runner.rs
new file mode 100644
index 0000000000000..b0d7360bcd879
--- /dev/null
+++ b/tests/pretty/custom-test-runner.rs
@@ -0,0 +1,25 @@
+//@ compile-flags: --crate-type=lib --test --remap-path-prefix={{src-base}}/=/the/src/ --remap-path-prefix={{src-base}}\=/the/src/
+//@ pretty-compare-only
+//@ pretty-mode:expanded
+//@ pp-exact:custom-test-runner.pp
+
+// Example taken from the unstable book.
+
+#![feature(custom_test_frameworks)]
+#![test_runner(my_runner)]
+
+fn my_runner(tests: &[&i32]) {
+    for t in tests {
+        if **t == 0 {
+            println!("PASSED");
+        } else {
+            println!("FAILED");
+        }
+    }
+}
+
+#[test_case]
+const WILL_PASS: i32 = 0;
+
+#[test_case]
+const WILL_FAIL: i32 = 4;

From 95296e6c9628b9d1a5ca6bc107ea4f8e55380c24 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Fri, 18 Sep 2026 17:24:19 +0200
Subject: [PATCH 2/2] libtest harness: avoid 'extern crate test' with custom
 runner

---
 compiler/rustc_builtin_macros/src/test_harness.rs | 7 ++++++-
 tests/pretty/custom-test-runner.pp                | 1 -
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_builtin_macros/src/test_harness.rs b/compiler/rustc_builtin_macros/src/test_harness.rs
index 677db66530ecb..bd2ea5a3e6696 100644
--- a/compiler/rustc_builtin_macros/src/test_harness.rs
+++ b/compiler/rustc_builtin_macros/src/test_harness.rs
@@ -364,7 +364,12 @@ fn add_main(cx: &mut TestCtxt<'_>, c: &mut ast::Crate) {
     });
 
     // Integrate the new item into existing module structures.
-    let items = AstFragment::Items(smallvec![test_extern_stmt, main]);
+    // `extern crate test;` is only needed with the default runner.
+    let items = AstFragment::Items(if cx.test_runner.is_none() {
+        smallvec![test_extern_stmt, main]
+    } else {
+        smallvec![main]
+    });
     c.items.extend(cx.ext_cx.monotonic_expander().fully_expand_fragment(items).make_items());
 }
 
diff --git a/tests/pretty/custom-test-runner.pp b/tests/pretty/custom-test-runner.pp
index dc777e37e3041..5965d76bbc8a5 100644
--- a/tests/pretty/custom-test-runner.pp
+++ b/tests/pretty/custom-test-runner.pp
@@ -26,7 +26,6 @@
 pub const WILL_PASS: i32 = 0;
 #[rustc_test_marker = "WILL_FAIL"]
 pub const WILL_FAIL: i32 = 4;
-extern crate test;
 #[rustc_main]
 #[coverage(off)]
 #[doc(hidden)]