Move tmpdir test helper to test helpers file

test/unit/constants.test.ts

@@ -1,5 +1,3 @@
-import * as fs from "fs"
-import { tmpdir } from "../../test/utils/constants"
 import { loggerModule } from "../utils/helpers"
 
 // jest.mock is hoisted above the imports so we must use `require` here.
@@ -89,16 +87,3 @@ describe("constants", () => {
     })
   })
 })
-
-describe("test constants", () => {
-  describe("tmpdir", () => {
-    it("should return a temp directory", async () => {
-      const testName = "temp-dir"
-      const pathToTempDir = await tmpdir(testName)
-
-      expect(pathToTempDir).toContain(testName)
-
-      await fs.promises.rmdir(pathToTempDir)
-    })
-  })
-})

test/unit/helpers.test.ts

@@ -0,0 +1,14 @@
+import { promises as fs } from "fs"
+import { tmpdir } from "../../test/utils/helpers"
+
+/**
+ * This file is for testing test helpers (not core code).
+ */
+describe("test helpers", () => {
+  it("should return a temp directory", async () => {
+    const testName = "temp-dir"
+    const pathToTempDir = await tmpdir(testName)
+    expect(pathToTempDir).toContain(testName)
+    expect(fs.access(pathToTempDir)).resolves.toStrictEqual(undefined)
+  })
+})