fix: Do not warn tests outside a module for integration tests

Fixes #11024

Author: berkus

clippy_lints/src/tests_outside_test_module.rs

@@ -5,7 +5,9 @@ use rustc_hir::{Body, FnDecl};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::declare_lint_pass;
 use rustc_span::def_id::LocalDefId;
-use rustc_span::Span;
+use rustc_span::source_map::SourceMap;
+use rustc_span::{FileName, RealFileName, Span};
+use std::path::Component;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -15,6 +17,7 @@ declare_clippy_lint! {
     /// ### Why restrict this?
     /// The idiomatic (and more performant) way of writing tests is inside a testing module (flagged with `#[cfg(test)]`),
     /// having test functions outside of this module is confusing and may lead to them being "hidden".
+    /// This does not apply to integration tests though, and this lint will ignore those.
     ///
     /// ### Example
     /// ```no_run
@@ -59,6 +62,7 @@ impl LateLintPass<'_> for TestsOutsideTestModule {
     ) {
         if !matches!(kind, FnKind::Closure)
             && is_in_test_function(cx.tcx, body.id().hir_id)
+            && !is_integration_test(cx.tcx.sess.source_map(), sp)
             && !is_in_cfg_test(cx.tcx, body.id().hir_id)
         {
             #[expect(clippy::collapsible_span_lint_calls, reason = "rust-clippy#7797")]
@@ -74,3 +78,12 @@ impl LateLintPass<'_> for TestsOutsideTestModule {
         }
     }
 }
+
+fn is_integration_test(sm: &SourceMap, sp: Span) -> bool {
+    match sm.span_to_filename(sp) {
+        FileName::Real(RealFileName::LocalPath(name)) => {
+            name.components().next() == Some(Component::Normal("tests".as_ref()))
+        },
+        _ => false,
+    }
+}

tests/ui/tests_outside_test_module.rs

@@ -5,11 +5,10 @@ fn main() {
     // test code goes here
 }
 
-// Should lint
+// Should not lint
+// Because we're inside an integration test
 #[test]
 fn my_test() {}
-//~^ ERROR: this function marked with #[test] is outside a #[cfg(test)] module
-//~| NOTE: move it to a testing module marked with #[cfg(test)]
 
 #[cfg(test)]
 mod tests {