[Tests] add initial enzyme-adapter-utils unit tests

packages/enzyme-test-suite/test/adapter-utils-spec.jsx

@@ -0,0 +1,22 @@
+import { expect } from 'chai';
+import { ensureKeyOrUndefined } from 'enzyme-adapter-utils';
+
+describe('enzyme-adapter-utils', () => {
+  describe('ensureKeyOrUndefined', () => {
+    it('returns the key if truthy', () => {
+      [true, 42, 'foo', [], {}, () => {}].forEach((truthy) => {
+        expect(ensureKeyOrUndefined(truthy)).to.equal(truthy);
+      });
+    });
+
+    it('returns the empty string if the key is the empty string', () => {
+      expect(ensureKeyOrUndefined('')).to.equal('');
+    });
+
+    it('returns undefined if falsy and not the empty string', () => {
+      [null, undefined, false, 0, NaN].forEach((falsy) => {
+        expect(ensureKeyOrUndefined(falsy)).to.equal(undefined);
+      });
+    });
+  });
+});