diff --git a/knip.json b/knip.json
index b37bb19..8d7acb0 100644
--- a/knip.json
+++ b/knip.json
@@ -1,5 +1,5 @@
 {
   "$schema": "https://unpkg.com/knip@6/schema.json",
-  "entry": ["scripts/*.mjs"],
+  "entry": ["scripts/*.mjs", "src/**/*.test-d.ts"],
   "project": ["src/**/*.ts", "scripts/*.mjs"]
 }
diff --git a/src/__tests__/index.ts b/src/__tests__/index.test.ts
similarity index 100%
rename from src/__tests__/index.ts
rename to src/__tests__/index.test.ts
diff --git a/src/__tests__/path-parts.ts b/src/__tests__/path-parts.test.ts
similarity index 100%
rename from src/__tests__/path-parts.ts
rename to src/__tests__/path-parts.test.ts
diff --git a/src/__tests__/properties.ts b/src/__tests__/properties.test.ts
similarity index 100%
rename from src/__tests__/properties.ts
rename to src/__tests__/properties.test.ts
diff --git a/vitest.config.mts b/vitest.config.mts
index c1ab2d0..e235735 100644
--- a/vitest.config.mts
+++ b/vitest.config.mts
@@ -1,17 +1,8 @@
-import {configDefaults, defineConfig, type ViteUserConfig} from 'vitest/config'
+import {defineConfig, type ViteUserConfig} from 'vitest/config'
 
 const config: ViteUserConfig = defineConfig({
   test: {
-    include: ['src/**/__tests__/**/*.ts'],
-    exclude: [
-      ...configDefaults.exclude,
-      // Shared helpers, not a test file.
-      'src/__tests__/utils.ts',
-      // Type tests: `npm run typecheck` checks them. At runtime every
-      // `expectTypeOf` call is a no-op, so they would pass without testing
-      // anything.
-      'src/**/*.test-d.ts',
-    ],
+    include: ['src/**/__tests__/**/*.test.ts'],
     coverage: {
       provider: 'v8',
       include: ['src/**/*.ts'],