feat(diff-snapshot): clean up test results from previous test runs fo…

…r a given snapshot

__tests__/integration.spec.js

@@ -140,5 +140,26 @@ describe('toMatchImageSnapshot', () => {
       // just because file was written does not mean it is a png image
       expect(isPng(imageBuffer)).toBe(true);
     });
+
+    it('removes result image from previous test runs for the same snapshot', () => {
+      const customSnapshotIdentifier = getIdentifierIndicatingCleanupIsRequired();
+      const pathToResultImage = path.join(__dirname, diffOutputDir(), `${customSnapshotIdentifier}-diff.png`);
+      // First we need to write a new snapshot image
+      expect(
+        () => expect(imageData).toMatchImageSnapshot({ customSnapshotIdentifier })
+      ).not.toThrowError();
+
+      // then test against a different image (to generate a results image)
+      expect(
+        () => expect(failImageData).toMatchImageSnapshot({ customSnapshotIdentifier })
+      ).toThrow();
+
+      // then test against image that should not generate results image (as it is passing test)
+      expect(
+        () => expect(imageData).toMatchImageSnapshot({ customSnapshotIdentifier })
+      ).not.toThrowError();
+
+      expect(fs.existsSync(pathToResultImage)).toBe(false);
+    });
   });
 });

package.json

@@ -27,8 +27,13 @@
       "!**/node_modules/**",
       "!test-results/**"
     ],
-    "testMatch": ["<rootDir>/__tests__/**/*.js"],
-    "coveragePathIgnorePatterns": ["/node_modules/", "<rootDir>/examples"] 
+    "testMatch": [
+      "<rootDir>/__tests__/**/*.js"
+    ],
+    "coveragePathIgnorePatterns": [
+      "/node_modules/",
+      "<rootDir>/examples"
+    ]
   },
   "repository": {
     "type": "git",
@@ -42,17 +47,16 @@
     "eslint-config-amex": "^7.0.0",
     "is-png": "^1.1.0",
     "jest": "^22.0.0",
-    "lodash": "^4.17.4",
-    "mock-spawn": "^0.2.6",
-    "rimraf": "^2.6.2"
+    "mock-spawn": "^0.2.6"
   },
   "dependencies": {
     "chalk": "^1.1.3",
     "get-stdin": "^5.0.1",
     "lodash": "^4.17.4",
     "mkdirp": "^0.5.1",
     "pixelmatch": "^4.0.2",
-    "pngjs": "^3.3.0"
+    "pngjs": "^3.3.0",
+    "rimraf": "^2.6.2"
   },
   "peerDependencies": {
     "jest": ">=20 <=22"

src/diff-snapshot.js

@@ -15,6 +15,7 @@
 const fs = require('fs');
 const path = require('path');
 const childProcess = require('child_process');
+const rimraf = require('rimraf');
 const pixelmatch = require('pixelmatch');
 const mkdirp = require('mkdirp');
 const { PNG } = require('pngjs');
@@ -35,6 +36,9 @@ function diffImageToSnapshot(options) {
   if (fs.existsSync(baselineSnapshotPath) && !updateSnapshot) {
     const outputDir = path.join(snapshotsDir, '__diff_output__');
     const diffOutputPath = path.join(outputDir, `${snapshotIdentifier}-diff.png`);
+
+    rimraf.sync(diffOutputPath);
+
     const defaultDiffConfig = {
       threshold: 0.01,
     };