Suggestion of test to automate bug detection

dubzzz · Feb 20, 2019 · 114022f · 114022f
1 parent 04ebef5
commit 114022f
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Showing 3 changed files with 34 additions and 1 deletion.
diff --git a/package.json b/package.json
@@ -36,6 +36,7 @@
     "eslint-plugin-react": "^7.1.0",
     "eslint-plugin-relay": "~0.0.19",
     "execa": "^1.0.0",
+    "fast-check": "^1.10.1",
     "flow-bin": "^0.93.0",
     "glob": "^7.1.1",
     "graceful-fs": "^4.1.15",

diff --git a/packages/expect/src/__tests__/matchers.test.js b/packages/expect/src/__tests__/matchers.test.js
@@ -11,6 +11,7 @@ const jestExpect = require('../');
 const Immutable = require('immutable');
 const chalk = require('chalk');
 const chalkEnabled = chalk.enabled;
+const fc = require('fast-check');
 
 beforeAll(() => {
   chalk.enabled = true;
@@ -289,6 +290,17 @@ describe('.toStrictEqual()', () => {
     expect([{a: [{a: undefined}]}]).not.toStrictEqual([{a: [{}]}]);
   });
 
+  fit('distinguishes distinct values', () => {
+    // Given a and b values such as a different from b
+    // We expect `expect(a).not.toStrictEqual(b)`
+    fc.assert(
+      fc.property(fc.anything(), fc.anything(), (a, b) => {
+        fc.pre(JSON.stringify(a) !== JSON.stringify(b));
+        expect(a).not.toStrictEqual(b);
+      }),
+    );
+  });
+
   it('passes when comparing same type', () => {
     expect({
       test: new TestClassA(1, 2),

diff --git a/yarn.lock b/yarn.lock
@@ -5544,6 +5544,14 @@ fancy-log@^1.3.2:
     parse-node-version "^1.0.0"
     time-stamp "^1.0.0"
 
+fast-check@^1.10.1:
+  version "1.10.1"
+  resolved "https://registry.yarnpkg.com/fast-check/-/fast-check-1.10.1.tgz#a2f8f45269c85c44c700fad20cc6cfa804795c36"
+  integrity sha512-7TTA4QMpoSUX5nbwsOfSQAOllKFUA3FWzlTIT7V57ZN/Ju6q/wCeRXDkygNI0nVAEfPeva+fPlPlbAqizCXIUw==
+  dependencies:
+    lorem-ipsum "~1.0.6"
+    pure-rand "^1.6.2"
+
 fast-deep-equal@^2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/fast-deep-equal/-/fast-deep-equal-2.0.1.tgz#7b05218ddf9667bf7f370bf7fdb2cb15fdd0aa49"
@@ -8347,6 +8355,13 @@ loose-envify@^1.0.0, loose-envify@^1.1.0, loose-envify@^1.3.1:
   dependencies:
     js-tokens "^3.0.0 || ^4.0.0"
 
+lorem-ipsum@~1.0.6:
+  version "1.0.6"
+  resolved "https://registry.yarnpkg.com/lorem-ipsum/-/lorem-ipsum-1.0.6.tgz#69e9ab02bbb0991915d71b5559fe016d526f013f"
+  integrity sha512-Rx4XH8X4KSDCKAVvWGYlhAfNqdUP5ZdT4rRyf0jjrvWgtViZimDIlopWNfn/y3lGM5K4uuiAoY28TaD+7YKFrQ==
+  dependencies:
+    minimist "~1.2.0"
+
 loud-rejection@^1.0.0:
   version "1.6.0"
   resolved "https://registry.yarnpkg.com/loud-rejection/-/loud-rejection-1.6.0.tgz#5b46f80147edee578870f086d04821cf998e551f"
@@ -8901,7 +8916,7 @@ minimist@0.0.8:
   resolved "https://registry.yarnpkg.com/minimist/-/minimist-0.0.8.tgz#857fcabfc3397d2625b8228262e86aa7a011b05d"
   integrity sha1-hX/Kv8M5fSYluCKCYuhqp6ARsF0=
 
-minimist@1.2.0, minimist@^1.1.1, minimist@^1.1.3, minimist@^1.2.0:
+minimist@1.2.0, minimist@^1.1.1, minimist@^1.1.3, minimist@^1.2.0, minimist@~1.2.0:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/minimist/-/minimist-1.2.0.tgz#a35008b20f41383eec1fb914f4cd5df79a264284"
   integrity sha1-o1AIsg9BOD7sH7kU9M1d95omQoQ=
@@ -10637,6 +10652,11 @@ punycode@^2.1.0:
   resolved "https://registry.yarnpkg.com/punycode/-/punycode-2.1.1.tgz#b58b010ac40c22c5657616c8d2c2c02c7bf479ec"
   integrity sha512-XRsRjdf+j5ml+y/6GKHPZbrF/8p2Yga0JPtdqTIY2Xe5ohJPD9saDJJLPvp9+NSBprVvevdXZybnj2cv8OEd0A==
 
+pure-rand@^1.6.2:
+  version "1.6.2"
+  resolved "https://registry.yarnpkg.com/pure-rand/-/pure-rand-1.6.2.tgz#90b3ae78efe36f7e6e27bfffedf934f77382e6e6"
+  integrity sha512-HNwHOH63m7kCxe0kWEe5jSLwJiL2N83RUUN8POniFuZS+OsbFcMWlvXgxIU2nwKy2zYG2bQan40WBNK4biYPRg==
+
 q@0.9.7:
   version "0.9.7"
   resolved "https://registry.yarnpkg.com/q/-/q-0.9.7.tgz#4de2e6cb3b29088c9e4cbc03bf9d42fb96ce2f75"