Improve mutation test

package.json

@@ -45,6 +45,7 @@
     "gitbook-cli": "^2.3.0",
     "istanbul": "^0.4.5",
     "mocha": "^3.4.2",
+    "sinon": "^2.3.5",
     "stryker": "^0.6.6",
     "stryker-api": "^0.5.5",
     "stryker-html-reporter": "^0.4.6",

stryker.conf.js

@@ -3,10 +3,9 @@ module.exports = function(config) {
         files: [
             { pattern: 'lib/*.js', mutated: true, included: false},
             { pattern: 'specs/*.js', mutated: false, included: false},
-            { pattern: 'lib/util/*.js', mutated: false, included: false},
+            { pattern: 'lib/util/*.js', mutated: true, included: false},
             { pattern: 'lib/test/*.js', mutated: false, included: false},
-            'test/*.js',
-            'test/utils.js'
+            'test/**/*.js'
         ],
         testRunner: 'mocha',
         testFramework: 'mocha',

test/assert.js

@@ -9,6 +9,7 @@ const {isString} = s.utils;
 describe('Test the assert functions', () => {
 
     it('should set and get the checkAsserts', () => {
+        expect(s.isCheckAsserts()).to.be.false;	// default false
         s.checkAsserts(true);
         expect(s.isCheckAsserts()).to.be.true;
         s.checkAsserts(false);

test/exerciseFn.js

@@ -11,5 +11,7 @@ describe('Test the exerciseFn function', () => {
             args: s.cat(':x', isInteger),
             ret: isInteger
         });
+
+        expect(s.exerciseFn(square, 7)).to.have.length(7);
     });
 });

test/explain.js

@@ -1,10 +1,18 @@
 const {expect} = require('chai');;
+const sinon = require('sinon');
 
 const s = require('../lib/spec');
 
 const {isString} = s.utils;
 
 describe('Test the explain function', () => {
+    it('should return the explanation string success', () => {
+        const stub = sinon.stub(process.stdout, 'write');
+        s.explain(isString, 'foobar');
+        stub.restore();
+        expect(stub.calledWith('Success!\n')).to.be.true;
+    });
+
     it('should return the explanation string success', () => {
         expect(s.explainStr(isString, 'foobar')).to.equal('Success!\n');
     });

test/isIntInRange.js

@@ -17,6 +17,10 @@ describe('Test isIntInRange? function', () => {
         expect(s.isIntInRange(0, 13, -42)).to.be.false;
     });
 
+    it('should have an upper bound that is larger than the lower bound', () => {
+        expect(s.isIntInRange(13, 0, 0)).to.be.false;
+    });
+
     it('should use the spec to test', () => {
         expect(check(s.isIntInRange, '../specs/intInRange')).to.have.property('result').to.equal(true);        
     });