red_knot: add explicit test for concise reveal_type diagnostic

This test reflects the status quo before we change things.

crates/red_knot/tests/cli.rs

@@ -1052,6 +1052,39 @@ fn concise_diagnostics() -> anyhow::Result<()> {
     Ok(())
 }
 
+/// This tests the diagnostic format for revealed type.
+///
+/// This test was introduced because changes were made to
+/// how the revealed type diagnostic was constructed and
+/// formatted in "verbose" mode. But it required extra
+/// logic to ensure the concise version didn't regress on
+/// information content. So this test was introduced to
+/// capture that.
+#[test]
+fn concise_revealed_type() -> anyhow::Result<()> {
+    let case = TestCase::with_file(
+        "test.py",
+        r#"
+        from typing_extensions import reveal_type
+
+        x = "hello"
+        reveal_type(x)
+        "#,
+    )?;
+
+    assert_cmd_snapshot!(case.command().arg("--output-format=concise"), @r#"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    info[revealed-type] <temp_dir>/test.py:5:1: Revealed type is `Literal["hello"]`
+    Found 1 diagnostic
+
+    ----- stderr -----
+    "#);
+
+    Ok(())
+}
+
 struct TestCase {
     _temp_dir: TempDir,
     _settings_scope: SettingsBindDropGuard,