test(keys): add keys function tests

src/__tests__/keys.spec.ts

@@ -0,0 +1,44 @@
+import keys from '../keys';
+
+describe('keys', () => {
+  test('should return an array of the objects keys', () => {
+    const obj = {
+      a: 1,
+      b: 2,
+      c: 3,
+    };
+
+    expect(keys(obj)).toHaveLength(3);
+    expect(keys(obj)[0]).toBe('a');
+    expect(keys(obj)[1]).toBe('b');
+    expect(keys(obj)[2]).toBe('c');
+  });
+
+  test('should return deep object keys in dot notation if follow is true', () => {
+    const obj = {
+      a: 1,
+      b: {
+        c: 2,
+      },
+    };
+
+    expect(keys(obj, {
+      follow: false,
+    })[1]).toBe('b');
+    expect(keys(obj, {
+      follow: true,
+    })[1]).toBe('b.c');
+  });
+
+  test('', () => {
+    const invalidObj: unknown = 'testing';
+    const invalidFollow: unknown = 'testing';
+
+    expect(() => keys(invalidObj as OObject))
+      .toThrow(new TypeError('Expected Object, got string testing'));
+    expect(() => keys({}, {
+      follow: invalidFollow as boolean,
+    }))
+      .toThrow(new TypeError('Expected Boolean, got string testing'));
+  });
+});