add more tests for utils.deprecate (#3628)

* ensure coverage data not cached between execution calls to npm test

* wallaby: disable debug mode in and ignore lib/browser/ [ci skip]

* refactor utils.deprecate and add tests to get coverage up

- `utils.deprecate()` needs a non-empty message
- it no longer shims `process.emitWarning`, since we dropped Node v4 support
- added tests because coverage

.wallaby.js

@@ -17,7 +17,8 @@ module.exports = () => {
       },
       'package.json',
       'test/opts/mocha.opts',
-      'mocharc.yml'
+      'mocharc.yml',
+      '!lib/browser/**/*.js',
     ],
     filesWithNoCoverageCalculated: [
       'test/**/*.fixture.js',
@@ -52,7 +53,6 @@ module.exports = () => {
         return execFile.apply(this, arguments);
       };
       require('./test/setup');
-    },
-    debug: true
+    }
   };
 };

lib/utils.js

@@ -588,28 +588,20 @@ exports.getError = function(err) {
  *
  * @param {string} msg
  */
-exports.deprecate = function(msg) {
+exports.deprecate = function deprecate(msg) {
   msg = String(msg);
-  if (seenDeprecationMsg.hasOwnProperty(msg)) {
-    return;
-  }
-  seenDeprecationMsg[msg] = true;
-  doDeprecationWarning(msg);
-};
-
-var seenDeprecationMsg = {};
-
-var doDeprecationWarning = process.emitWarning
-  ? function(msg) {
-      // Node.js v6+
+  if (msg && !deprecate.cache[msg]) {
+    deprecate.cache[msg] = true;
+    if (process.emitWarning) {
       process.emitWarning(msg, 'DeprecationWarning');
-    }
-  : function(msg) {
-      // Everything else
+    } else {
       process.nextTick(function() {
         console.warn(msg);
       });
-    };
+    }
+  }
+};
+exports.deprecate.cache = {};
 
 /**
  * @summary

package-scripts.js

@@ -69,7 +69,7 @@ module.exports = {
       },
       node: {
         default: {
-          script: `nps ${[
+          script: `rimraf .nyc_output && nps ${[
             'build',
             'test.node.bdd',
             'test.node.tdd',

test/unit/utils.spec.js

@@ -1,8 +1,19 @@
 'use strict';
 
 var utils = require('../../lib/utils');
+var sinon = require('sinon');
 
 describe('lib/utils', function() {
+  var sandbox;
+
+  beforeEach(function() {
+    sandbox = sinon.createSandbox();
+  });
+
+  afterEach(function() {
+    sandbox.restore();
+  });
+
   describe('clean', function() {
     it('should remove the wrapping function declaration', function() {
       expect(
@@ -618,4 +629,44 @@ describe('lib/utils', function() {
       expect(utils.escape('💩'), 'to be', '💩');
     });
   });
+
+  describe('deprecate', function() {
+    var emitWarning;
+
+    beforeEach(function() {
+      if (process.emitWarning) {
+        emitWarning = process.emitWarning;
+        sandbox.stub(process, 'emitWarning');
+      } else {
+        process.emitWarning = sandbox.spy();
+      }
+      utils.deprecate.cache = {};
+    });
+
+    afterEach(function() {
+      // if this is not set, then we created it, so we should remove it.
+      if (!emitWarning) {
+        delete process.emitWarning;
+      }
+    });
+
+    it('should coerce its parameter to a string', function() {
+      utils.deprecate(1);
+      expect(process.emitWarning, 'to have a call satisfying', [
+        '1',
+        'DeprecationWarning'
+      ]);
+    });
+
+    it('should cache the message', function() {
+      utils.deprecate('foo');
+      utils.deprecate('foo');
+      expect(process.emitWarning, 'was called times', 1);
+    });
+
+    it('should ignore falsy messages', function() {
+      utils.deprecate('');
+      expect(process.emitWarning, 'was not called');
+    });
+  });
 });