Asserting undefined value intentionally (#144)

* asserting undefined value

* adding enzyme-matchers undefined value tests

packages/enzyme-matchers/src/assertions/__tests__/toHaveProp--tests.js

@@ -110,6 +110,20 @@ describe('toHaveProp', () => {
         expect(pass).toBeTruthy();
         expect(fail).toBeFalsy();
       });
+
+      it('works without a prop value', () => {
+        const wrapper = builder(<Fixture />);
+        const truthy = toHaveProp(wrapper.find(User), 'name');
+
+        expect(truthy.pass).toBeTruthy();
+      });
+
+      it('works with undefined value', () => {
+        const wrapper = builder(<Fixture />);
+        const falsy = toHaveProp(wrapper.find(User), 'name', undefined);
+
+        expect(falsy.pass).toBeFalsy();
+      });
     });
   });
 });

packages/enzyme-matchers/src/assertions/__tests__/toHaveState--tests.js

@@ -89,6 +89,20 @@ describe('toHaveState', () => {
         expect(truthyResults.pass).toBeTruthy();
         expect(falsyResults.pass).toBeFalsy();
       });
+
+      it('works without a prop value', () => {
+        const wrapper = builder(<Fixture />);
+        const truthy = toHaveState(wrapper, 'foo');
+
+        expect(truthy.pass).toBeTruthy();
+      });
+
+      it('works with undefined value', () => {
+        const wrapper = builder(<Fixture />);
+        const falsy = toHaveState(wrapper, 'foo', undefined);
+
+        expect(falsy.pass).toBeFalsy();
+      });
     });
   });
 });

packages/enzyme-matchers/src/assertions/toHaveProp.js

@@ -18,7 +18,6 @@ function toHaveProp(
   propValue?: any
 ): Matcher {
   const props = enzymeWrapper.props();
-
   const contextualInformation = {
     actual: `Actual: ${stringify({ [propKey]: props[propKey] })}`,
     expected: `Expected: ${stringify({ [propKey]: propValue })}`,
@@ -37,8 +36,8 @@ function toHaveProp(
   }
 
   // key exists given above check, and we're not validating over values,
-  // so its always true
-  if (propValue === undefined) {
+  // so its always true unless the undefined value was provided explicitly
+  if (propValue === undefined && arguments.length === 2) {
     return {
       pass: true,
       message: `Expected wrapper to have any value for the prop "${propKey}"`,

packages/enzyme-matchers/src/assertions/toHaveState.js

@@ -37,8 +37,8 @@ function toHaveState(
   }
 
   // key exists given above check, and we're not validating over values,
-  // so its always true
-  if (stateValue === undefined) {
+  // so its always true unless the undefined value was provided explicitly
+  if (stateValue === undefined && arguments.length === 2) {
     return {
       pass: true,
       message: `Expected <${name(

packages/jest-enzyme/src/__failing_tests__/toHaveProp.test.js

@@ -16,4 +16,11 @@ describe('failing test', () => {
   it('fails NOT toHaveProp', () => {
     expect(shallow(<Fixture disabled />)).not.toHaveProp('disabled', true);
   });
+
+  it('fails toHaveProp undefined value', () => {
+    expect(shallow(<Fixture disabled={'value'} />)).toHaveProp(
+      'enabled',
+      undefined
+    );
+  });
 });

packages/jest-enzyme/src/__failing_tests__/toHaveState.test.js

@@ -28,4 +28,8 @@ describe('failing test', () => {
 
     expect(shallow(<Fixture disabled />)).not.toHaveState('foo', true);
   });
+
+  it('fails toHaveState undefined value', () => {
+    expect(shallow(<Fixture />)).toHaveState('foo', undefined);
+  });
 });