de: fix chemical reaction arrow

Rules/Languages/de/SharedRules/general.yaml

@@ -1044,10 +1044,7 @@
   - bookmark: "@id"
   - test:
     - if: ".='→' or .='⟶'"
-      then_test:
-        if: "$Verbosity='Terse'"
-        then: [T: "formen"]      # phrase(hydrogen and oxygen 'forms' water )
-        else: [T: "reagiert auf die form"]      # phrase(hydrogen and oxygen 'reacts to form' water)
+      then: [T: "ergibt"]      # phrase(hydrogen and oxygen 'forms/reacts to form' water)
     - else_if: ".='⇌' or .='🣑'" # U+01F8D1
       then: [T: "ist im gleichgewicht mit"]      # phrase(a reactant 'is in equilibrium with' a product)
     - else_if: ".='🣓'" # U+1F8D3

tests/Languages/de/chemistry.rs

@@ -74,6 +74,32 @@ fn chemical_state_names_are_german_adjectives() -> Result<()> {
   Ok(())
 }
 
+#[test]
+fn reaction_arrow_uses_idiomatic_german() -> Result<()> {
+  // A reaction arrow should describe the resulting products idiomatically in German.
+  let expr = "<math><mrow>
+      <mn>2</mn><mi>H</mi><mi>Cl</mi><mo>+</mo><mn>2</mn><mtext>Na</mtext>
+      <mo>&#x2192;</mo>
+      <mn>2</mn><mtext>Na</mtext><mi>Cl</mi><mo>+</mo>
+      <msub><mi>H</mi><mn>2</mn></msub>
+    </mrow></math>";
+  test_prefs(
+    "de",
+    "SimpleSpeak",
+    vec![("Verbosity", "Terse")],
+    expr,
+    "2, groß h, groß c l; plus 2 groß n a; ergibt; 2, groß n a, groß c l; plus groß h, 2",
+  )?;
+  test_prefs(
+    "de",
+    "SimpleSpeak",
+    vec![("Verbosity", "Verbose")],
+    expr,
+    "2, groß h, groß c l; plus 2 groß n a; ergibt; 2, groß n a, groß c l; plus groß h, index 2",
+  )?;
+  Ok(())
+}
+
 
 /* // ignored below
 #[test]