diff --git a/src/def/lower.rs b/src/def/lower.rs
index b169aa1..6e15b4a 100644
--- a/src/def/lower.rs
+++ b/src/def/lower.rs
@@ -247,3 +247,132 @@ impl LowerCtx {
         self.alloc_expr(Expr::StringInterpolation(parts), ptr)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::lower;
+    use crate::base::{FileId, InFile};
+    use expect_test::{expect, Expect};
+    use std::fmt::Write;
+    use syntax::parse_file;
+
+    fn check_lower(src: &str, expect: Expect) {
+        let parse = parse_file(src);
+        let (module, _source_map) = lower(InFile::new(FileId(0), parse.root()));
+        let mut got = String::new();
+        for (i, e) in module.exprs.iter() {
+            writeln!(got, "{}: {:?}", i.into_raw(), e).unwrap();
+        }
+        expect.assert_eq(&got);
+    }
+
+    #[test]
+    fn literal() {
+        check_lower(
+            "42",
+            expect![[r#"
+                0: Literal(Int(42))
+            "#]],
+        );
+        check_lower(
+            "1.2e3",
+            expect![[r#"
+                0: Literal(Float(OrderedFloat(1200.0)))
+            "#]],
+        );
+        check_lower(
+            "a:b",
+            expect![[r#"
+                0: Literal(String("a:b"))
+            "#]],
+        );
+    }
+
+    #[test]
+    fn path() {
+        check_lower(
+            "./.",
+            expect![[r#"
+                0: Literal(Path(Path { anchor: Relative(FileId(0)), supers: 0, raw_segments: "" }))
+            "#]],
+        );
+        check_lower(
+            "../.",
+            expect![[r#"
+                0: Literal(Path(Path { anchor: Relative(FileId(0)), supers: 1, raw_segments: "" }))
+            "#]],
+        );
+        check_lower(
+            "../a/../../.b/./c",
+            expect![[r#"
+                0: Literal(Path(Path { anchor: Relative(FileId(0)), supers: 2, raw_segments: ".b/c" }))
+            "#]],
+        );
+        check_lower(
+            "/../a/../../.b/./c",
+            expect![[r#"
+                0: Literal(Path(Path { anchor: Absolute, supers: 0, raw_segments: ".b/c" }))
+            "#]],
+        );
+        check_lower(
+            "~/../a/../../.b/./c",
+            expect![[r#"
+                0: Literal(Path(Path { anchor: Home, supers: 2, raw_segments: ".b/c" }))
+            "#]],
+        );
+        check_lower(
+            "<p/../a/../../.b/./c>",
+            expect![[r#"
+                0: Literal(Path(Path { anchor: Search("p"), supers: 2, raw_segments: ".b/c" }))
+            "#]],
+        );
+    }
+
+    #[test]
+    fn lambda() {
+        check_lower(
+            "a: 0",
+            expect![[r#"
+                0: Literal(Int(0))
+                1: Lambda(Some(Idx::<NameDef>(0)), None, Idx::<Expr>(0))
+            "#]],
+        );
+        check_lower(
+            "{ }: 0",
+            expect![[r#"
+                0: Literal(Int(0))
+                1: Lambda(None, Some(Pat { fields: [], ellipsis: false }), Idx::<Expr>(0))
+            "#]],
+        );
+        check_lower(
+            "a@{ ... }: 0",
+            expect![[r#"
+                0: Literal(Int(0))
+                1: Lambda(Some(Idx::<NameDef>(0)), Some(Pat { fields: [], ellipsis: true }), Idx::<Expr>(0))
+            "#]],
+        );
+        check_lower(
+            "{ }@a: 0",
+            expect![[r#"
+                0: Literal(Int(0))
+                1: Lambda(Some(Idx::<NameDef>(0)), Some(Pat { fields: [], ellipsis: false }), Idx::<Expr>(0))
+            "#]],
+        );
+        check_lower(
+            "{ a, b ? 0, ... }: 0",
+            expect![[r#"
+                0: Literal(Int(0))
+                1: Literal(Int(0))
+                2: Lambda(None, Some(Pat { fields: [(Some(Idx::<NameDef>(0)), None), (Some(Idx::<NameDef>(1)), Some(Idx::<Expr>(0)))], ellipsis: true }), Idx::<Expr>(1))
+            "#]],
+        );
+        check_lower(
+            "{ a ? 0, b }@c: 0",
+            expect![[r#"
+                0: Literal(Int(0))
+                1: Literal(Int(0))
+                2: Lambda(Some(Idx::<NameDef>(0)), Some(Pat { fields: [(Some(Idx::<NameDef>(1)), Some(Idx::<Expr>(0))), (Some(Idx::<NameDef>(2)), None)], ellipsis: false }), Idx::<Expr>(1))
+            "#]],
+        );
+    }
+}
diff --git a/src/def/tests/mod.rs b/src/def/tests.rs
similarity index 98%
rename from src/def/tests/mod.rs
rename to src/def/tests.rs
index 511b2f4..a93e872 100644
--- a/src/def/tests/mod.rs
+++ b/src/def/tests.rs
@@ -2,8 +2,6 @@ use super::DefDatabase;
 use crate::tests::TestDB;
 use expect_test::expect;
 
-mod lower;
-
 #[test]
 fn source_map() {
     let (db, root_id) = TestDB::from_file("foo 123");
diff --git a/src/def/tests/lower.rs b/src/def/tests/lower.rs
deleted file mode 100644
index a13b854..0000000
--- a/src/def/tests/lower.rs
+++ /dev/null
@@ -1,125 +0,0 @@
-use crate::base::{FileId, InFile};
-use crate::def::lower::lower;
-use expect_test::{expect, Expect};
-use std::fmt::Write;
-use syntax::parse_file;
-
-fn check_lower(src: &str, expect: Expect) {
-    let parse = parse_file(src);
-    let (module, _source_map) = lower(InFile::new(FileId(0), parse.root()));
-    let mut got = String::new();
-    for (i, e) in module.exprs.iter() {
-        writeln!(got, "{}: {:?}", i.into_raw(), e).unwrap();
-    }
-    expect.assert_eq(&got);
-}
-
-#[test]
-fn literal() {
-    check_lower(
-        "42",
-        expect![[r#"
-            0: Literal(Int(42))
-        "#]],
-    );
-    check_lower(
-        "1.2e3",
-        expect![[r#"
-            0: Literal(Float(OrderedFloat(1200.0)))
-        "#]],
-    );
-    check_lower(
-        "a:b",
-        expect![[r#"
-            0: Literal(String("a:b"))
-        "#]],
-    );
-}
-
-#[test]
-fn path() {
-    check_lower(
-        "./.",
-        expect![[r#"
-            0: Literal(Path(Path { anchor: Relative(FileId(0)), supers: 0, raw_segments: "" }))
-        "#]],
-    );
-    check_lower(
-        "../.",
-        expect![[r#"
-            0: Literal(Path(Path { anchor: Relative(FileId(0)), supers: 1, raw_segments: "" }))
-        "#]],
-    );
-    check_lower(
-        "../a/../../.b/./c",
-        expect![[r#"
-            0: Literal(Path(Path { anchor: Relative(FileId(0)), supers: 2, raw_segments: ".b/c" }))
-        "#]],
-    );
-    check_lower(
-        "/../a/../../.b/./c",
-        expect![[r#"
-            0: Literal(Path(Path { anchor: Absolute, supers: 0, raw_segments: ".b/c" }))
-        "#]],
-    );
-    check_lower(
-        "~/../a/../../.b/./c",
-        expect![[r#"
-            0: Literal(Path(Path { anchor: Home, supers: 2, raw_segments: ".b/c" }))
-        "#]],
-    );
-    check_lower(
-        "<p/../a/../../.b/./c>",
-        expect![[r#"
-            0: Literal(Path(Path { anchor: Search("p"), supers: 2, raw_segments: ".b/c" }))
-        "#]],
-    );
-}
-
-#[test]
-fn lambda() {
-    check_lower(
-        "a: 0",
-        expect![[r#"
-            0: Literal(Int(0))
-            1: Lambda(Some(Idx::<NameDef>(0)), None, Idx::<Expr>(0))
-        "#]],
-    );
-    check_lower(
-        "{ }: 0",
-        expect![[r#"
-            0: Literal(Int(0))
-            1: Lambda(None, Some(Pat { fields: [], ellipsis: false }), Idx::<Expr>(0))
-        "#]],
-    );
-    check_lower(
-        "a@{ ... }: 0",
-        expect![[r#"
-            0: Literal(Int(0))
-            1: Lambda(Some(Idx::<NameDef>(0)), Some(Pat { fields: [], ellipsis: true }), Idx::<Expr>(0))
-        "#]],
-    );
-    check_lower(
-        "{ }@a: 0",
-        expect![[r#"
-            0: Literal(Int(0))
-            1: Lambda(Some(Idx::<NameDef>(0)), Some(Pat { fields: [], ellipsis: false }), Idx::<Expr>(0))
-        "#]],
-    );
-    check_lower(
-        "{ a, b ? 0, ... }: 0",
-        expect![[r#"
-            0: Literal(Int(0))
-            1: Literal(Int(0))
-            2: Lambda(None, Some(Pat { fields: [(Some(Idx::<NameDef>(0)), None), (Some(Idx::<NameDef>(1)), Some(Idx::<Expr>(0)))], ellipsis: true }), Idx::<Expr>(1))
-        "#]],
-    );
-    check_lower(
-        "{ a ? 0, b }@c: 0",
-        expect![[r#"
-            0: Literal(Int(0))
-            1: Literal(Int(0))
-            2: Lambda(Some(Idx::<NameDef>(0)), Some(Pat { fields: [(Some(Idx::<NameDef>(1)), Some(Idx::<Expr>(0))), (Some(Idx::<NameDef>(2)), None)], ellipsis: false }), Idx::<Expr>(1))
-        "#]],
-    );
-}