4 files changed, 73 insertions, 24 deletions

diff --git a/crates/ra_assists/src/assists/early_return.rs b/crates/ra_assists/src/assists/early_return.rs
index f7d7e12e7..b3d025340 100644
--- a/crates/ra_assists/src/assists/early_return.rs
+++ b/crates/ra_assists/src/assists/early_return.rs
@@ -1,26 +1,3 @@
-//! Assist: `convert_to_guarded_return`
-//!
-//! Replace a large conditional with a guarded return.
-//!
-//! ```text
-//! fn <|>main() {
-//!     if cond {
-//!         foo();
-//!         bar();
-//!     }
-//! }
-//! ```
-//! ->
-//! ```text
-//! fn main() {
-//!     if !cond {
-//!         return;
-//!     }
-//!     foo();
-//!     bar();
-//! }
-//! ```
-
 use std::ops::RangeInclusive;
 
 use hir::db::HirDatabase;
@@ -36,6 +13,26 @@ use crate::{
     AssistId,
 };
 
+// Assist: convert_to_guarded_return
+// Replace a large conditional with a guarded return.
+// ```
+// fn main() {
+//     <|>if cond {
+//         foo();
+//         bar();
+//     }
+// }
+// ```
+// ->
+// ```
+// fn main() {
+//     if !cond {
+//         return;
+//     }
+//     foo();
+//     bar();
+// }
+// ```
 pub(crate) fn convert_to_guarded_return(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let if_expr: ast::IfExpr = ctx.node_at_offset()?;
     let expr = if_expr.condition()?.expr()?;
diff --git a/crates/ra_assists/src/doc_tests.rs b/crates/ra_assists/src/doc_tests.rs
new file mode 100644
index 000000000..88e901517
--- /dev/null
+++ b/crates/ra_assists/src/doc_tests.rs
@@ -0,0 +1,23 @@
+//! Each assist definition has a special comment, which specifies docs and
+//! example.
+//!
+//! We collect all the example and write the as tests in this module.
+
+mod generated;
+
+use hir::mock::MockDatabase;
+use ra_db::FileRange;
+use ra_syntax::TextRange;
+use test_utils::{assert_eq_text, extract_offset};
+
+fn check(assist_id: &str, before: &str, after: &str) {
+    let (before_cursor_pos, before) = extract_offset(before);
+    let (db, _source_root, file_id) = MockDatabase::with_single_file(&before);
+    let frange = FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
+
+    let (_assist_id, action) =
+        crate::assists(&db, frange).into_iter().find(|(id, _)| id.id.0 == assist_id).unwrap();
+
+    let actual = action.edit.apply(&before);
+    assert_eq_text!(after, &actual);
+}
diff --git a/crates/ra_assists/src/doc_tests/generated.rs b/crates/ra_assists/src/doc_tests/generated.rs
new file mode 100644
index 000000000..e5f6910f1
--- /dev/null
+++ b/crates/ra_assists/src/doc_tests/generated.rs
@@ -0,0 +1,27 @@
+//! Generated file, do not edit by hand, see `crate/ra_tools/src/codegen`
+
+use super::check;
+
+#[test]
+fn doctest_convert_to_guarded_return() {
+    check(
+        "convert_to_guarded_return",
+        r#####"
+fn main() {
+    <|>if cond {
+        foo();
+        bar();
+    }
+}
+"#####,
+        r#####"
+fn main() {
+    if !cond {
+        return;
+    }
+    foo();
+    bar();
+}
+"#####,
+    )
+}
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index ab77b46a9..de576324f 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -7,6 +7,8 @@
 
 mod assist_ctx;
 mod marks;
+#[cfg(test)]
+mod doc_tests;
 
 use hir::db::HirDatabase;
 use itertools::Itertools;
@@ -36,7 +38,7 @@ pub struct AssistAction {
     pub target: Option<TextRange>,
 }
 
-/// Return all the assists eapplicable at the given position.
+/// Return all the assists applicable at the given position.
 ///
 /// Assists are returned in the "unresolved" state, that is only labels are
 /// returned, without actual edits.