Don't show warning from spied console.warn (#12946)

packages/babel-cli/test/index.js

@@ -274,10 +274,20 @@ fs.readdirSync(fixtureLoc).forEach(function (binName) {
 describe("util.js", () => {
   describe("chmod", () => {
     it("should warn the user if chmod fails", () => {
-      const spyConsoleWarn = jest.spyOn(console, "warn");
-      // should expect a string as first argument
+      const spyConsoleWarn = jest
+        .spyOn(console, "warn")
+        .mockImplementation(() => {});
+
+      // The first argument should be a string.
+      // The real reason chmod will fail is due to wrong permissions,
+      // but this is enough to cause a failure.
       chmod(100, "file.js");
+
       expect(spyConsoleWarn).toHaveBeenCalledTimes(1);
+      expect(spyConsoleWarn).toHaveBeenCalledWith(
+        "Cannot change permissions of file.js",
+      );
+
       spyConsoleWarn.mockRestore();
     });
   });