Add noColors option to matcher (#5)

feat(matcher): add noColors options

README.md

@@ -29,13 +29,17 @@ Jest matcher that performs image comparisons using [Blink-diff](https://github.c
 
 ### Optional configuration:
 
-`toMatchImageSnapshot()` takes an optional options object where you can provide your own [blink-diff configuration parameters](http://yahoo.github.io/blink-diff/#object-usage) and/or a custom snapshot identifier string:
+`toMatchImageSnapshot()` takes an optional options object where you can provide your own [blink-diff configuration parameters](http://yahoo.github.io/blink-diff/#object-usage) and/or a custom snapshot identifier string and/or forcing no styled output for possibly storing the results in a file:
 
 ```javascript
   it('should demonstrate this matcher`s usage with a custom blink-diff config', () => {
     ...
     const blinkDiffConfig = { perceptual: true };
-    expect(image).toMatchImageSnapshot({ customDiffConfig: blinkDiffConfig, customSnapshotIdentifier: 'customSnapshotName' });
+    expect(image).toMatchImageSnapshot({ 
+      customDiffConfig: blinkDiffConfig, 
+      customSnapshotIdentifier: 'customSnapshotName', 
+      noColors: true // the default is false
+    });
   });  
 ```
 

__tests__/src/__snapshots__/index.spec.js.snap

@@ -21,3 +21,8 @@ exports[`toMatchImageSnapshot should fail when snapshot has a difference beyond
 `;
 
 exports[`toMatchImageSnapshot should throw an error if used with .not matcher 1`] = `"Jest: \`.not\` cannot be used with \`.toMatchImageSnapshot()\`."`;
+
+exports[`toMatchImageSnapshot should use noColors options if passed as true and not style error message 2`] = `
+"Expected image to match or be a close match to snapshot.
+See diff for details: path/to/result.png"
+`;

__tests__/src/index.spec.js

@@ -68,6 +68,18 @@ describe('toMatchImageSnapshot', () => {
       .toThrowErrorMatchingSnapshot();
   });
 
+  it('should use noColors options if passed as true and not style error message', () => {
+    // code 1 is result too different: https://github.com/yahoo/blink-diff/blob/master/index.js#L267
+    const mockDiffResult = { updated: false, code: 1, diffOutputPath: 'path/to/result.png' };
+    setupMock(mockDiffResult);
+    const { toMatchImageSnapshot } = require('../../src/index');
+    expect.extend({ toMatchImageSnapshot });
+
+
+    expect(() => expect('pretendthisisanimagebuffer').toMatchImageSnapshot({ noColors: true }))
+      .toThrowErrorMatchingSnapshot();
+  });
+
   it('should use custom blink-diff configuration if passed in', () => {
     const mockTestContext = {
       testPath: 'path/to/test.spec.js',

src/index.js

@@ -15,15 +15,17 @@
 const kebabCase = require('lodash/kebabCase');
 const merge = require('lodash/merge');
 const path = require('path');
-const chalk = require('chalk');
+const Chalk = require('chalk').constructor;
 const { diffImageToSnapshot } = require('./diff-snapshot');
 
 function updateSnapshotState(oldSnapshotState, newSnapshotState) {
   return merge({}, oldSnapshotState, newSnapshotState);
 }
 
-function toMatchImageSnapshot(received, { customSnapshotIdentifier = '', customDiffConfig = {} } = {}) {
+function toMatchImageSnapshot(received, { customSnapshotIdentifier = '', customDiffConfig = {}, noColors = false } = {}) {
   const { testPath, currentTestName, isNot } = this;
+  const chalk = new Chalk({ enabled: !noColors });
+
   let { snapshotState } = this;
   if (isNot) { throw new Error('Jest: `.not` cannot be used with `.toMatchImageSnapshot()`.'); }