Add tests for haveStyleRule messages

test/__snapshots__/toHaveStyleRule.spec.js.snap

@@ -0,0 +1,10 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`message when property not found 1`] = `"Property not found: \\"a\\""`;
+
+exports[`message when value does not match 1`] = `
+"Expected background to match:
+  \\"red\\"
+Received:
+  \\"orange\\""
+`;

test/toHaveStyleRule.spec.js

@@ -23,6 +23,10 @@ const toHaveStyleRule = (component, property, value, options) => {
   expect(mount(component)).toHaveStyleRule(property, value, options)
 }
 
+test('message when property not found', () => {
+  expect(() => expect(null).toHaveStyleRule('a')).toThrowErrorMatchingSnapshot()
+})
+
 test('null', () => {
   expect(null).not.toHaveStyleRule('a', 'b')
 })
@@ -31,6 +35,17 @@ test('non-styled', () => {
   notToHaveStyleRule(<div />, 'a', 'b')
 })
 
+test('message when value does not match', () => {
+  const Wrapper = styled.section`background: orange;`
+
+  expect(() => {
+    expect(renderer.create(<Wrapper />).toJSON()).toHaveStyleRule(
+      'background',
+      'red'
+    )
+  }).toThrowErrorMatchingSnapshot()
+})
+
 test('basic', () => {
   const Wrapper = styled.section`
     padding: 4em;