Throw error when instanceof is passed something that is not a functio…

…n as constructor
chaijs · Jan 16, 2017 · 2c4fc89 · 2c4fc89
1 parent 877dde8
commit 2c4fc89
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Showing 4 changed files with 184 additions and 1 deletion.
diff --git a/lib/chai/core/assertions.js b/lib/chai/core/assertions.js
@@ -988,9 +988,28 @@ module.exports = function (chai, _) {
 
   function assertInstanceOf (constructor, msg) {
     if (msg) flag(this, 'message', msg);
+
+    var target = flag(this, 'object')
+    var validInstanceOfTarget = constructor === Object(constructor) && (
+        typeof constructor === 'function' ||
+        (typeof Symbol !== 'undefined' && typeof constructor[Symbol.hasInstance] === 'function')
+    );
+
+    if (!validInstanceOfTarget) {
+      var constructorType = constructor === null ? 'null' : typeof constructor;
+      throw new Error('The instanceof assertion needs a constructor but ' + constructorType + ' was given.');
+    }
+
+    var isInstanceOf;
+    try {
+        isInstanceOf = target instanceof constructor
+    } catch (err) {
+        throw new Error(target + ' instanceof ' + constructor + ' failed: ' + err.message + '.')
+    }
+
     var name = _.getName(constructor);
     this.assert(
-        flag(this, 'object') instanceof constructor
+        isInstanceOf
       , 'expected #{this} to be an instance of ' + name
       , 'expected #{this} to not be an instance of ' + name
     );

diff --git a/test/assert.js b/test/assert.js
@@ -141,6 +141,50 @@ describe('assert', function () {
     function Foo(){}
     assert.instanceOf(new Foo(), Foo);
 
+    err(function(){
+      assert.instanceOf(new Foo(), 1);
+    }, "The instanceof assertion needs a constructor but number was given.");
+
+    err(function(){
+      assert.instanceOf(new Foo(), 'batman');
+    }, "The instanceof assertion needs a constructor but string was given.");
+
+    err(function(){
+      assert.instanceOf(new Foo(), {});
+    }, "The instanceof assertion needs a constructor but object was given.");
+
+    err(function(){
+      assert.instanceOf(new Foo(), true);
+    }, "The instanceof assertion needs a constructor but boolean was given.");
+
+    err(function(){
+      assert.instanceOf(new Foo(), null);
+    }, "The instanceof assertion needs a constructor but null was given.");
+
+    err(function(){
+      assert.instanceOf(new Foo(), undefined);
+    }, "The instanceof assertion needs a constructor but undefined was given.");
+
+    var expectedError;
+    try {
+      t instanceof Thing;
+    } catch (err) {
+      errMsg = '[object Object] instanceof function Thing(){} failed: ' + err.message + '.';
+    }
+
+    err(function(){
+      function Thing(){};
+      var t = new Thing();
+      Thing.prototype = 1337;
+      assert.instanceOf(t, Thing);
+    }, expectedError);
+
+    if (typeof Symbol !== 'undefined') {
+        err(function(){
+          assert.instanceOf(new Foo(), Symbol());
+        }, "The instanceof assertion needs a constructor but symbol was given.");
+    }
+
     err(function () {
       assert.instanceOf(5, Foo);
     }, "expected 5 to be an instance of Foo");
@@ -156,6 +200,36 @@ describe('assert', function () {
     function Foo(){}
     assert.notInstanceOf(new Foo(), String);
 
+    err(function(){
+      assert.notInstanceOf(new Foo(), 1);
+    }, "The instanceof assertion needs a constructor but number was given.");
+
+    err(function(){
+      assert.notInstanceOf(new Foo(), 'batman');
+    }, "The instanceof assertion needs a constructor but string was given.");
+
+    err(function(){
+      assert.notInstanceOf(new Foo(), {});
+    }, "The instanceof assertion needs a constructor but object was given.");
+
+    err(function(){
+      assert.notInstanceOf(new Foo(), true);
+    }, "The instanceof assertion needs a constructor but boolean was given.");
+
+    err(function(){
+      assert.notInstanceOf(new Foo(), null);
+    }, "The instanceof assertion needs a constructor but null was given.");
+
+    err(function(){
+      assert.notInstanceOf(new Foo(), undefined);
+    }, "The instanceof assertion needs a constructor but undefined was given.");
+
+    if (typeof Symbol !== 'undefined') {
+        err(function(){
+          assert.notInstanceOf(new Foo(), Symbol());
+        }, "The instanceof assertion needs a constructor but symbol was given.");
+    }
+
     err(function () {
       assert.notInstanceOf(new Foo(), Foo);
     }, "expected {} to not be an instance of Foo");

diff --git a/test/expect.js b/test/expect.js
@@ -366,6 +366,51 @@ describe('expect', function () {
     function Foo(){}
     expect(new Foo()).to.be.an.instanceof(Foo);
 
+    err(function(){
+      expect(new Foo()).to.an.instanceof(1);
+    }, "The instanceof assertion needs a constructor but number was given.");
+
+    err(function(){
+      expect(new Foo()).to.an.instanceof('batman');
+    }, "The instanceof assertion needs a constructor but string was given.");
+
+    err(function(){
+      expect(new Foo()).to.an.instanceof({});
+    }, "The instanceof assertion needs a constructor but object was given.");
+
+    err(function(){
+      expect(new Foo()).to.an.instanceof(true);
+    }, "The instanceof assertion needs a constructor but boolean was given.");
+
+    err(function(){
+      expect(new Foo()).to.an.instanceof(null);
+    }, "The instanceof assertion needs a constructor but null was given.");
+
+    err(function(){
+      expect(new Foo()).to.an.instanceof(undefined);
+    }, "The instanceof assertion needs a constructor but undefined was given.");
+
+    // Different browsers may have different error messages
+    var expectedError;
+    try {
+      t instanceof Thing;
+    } catch (err) {
+      errMsg = '[object Object] instanceof function Thing(){} failed: ' + err.message + '.';
+    }
+
+    err(function(){
+      function Thing(){};
+      var t = new Thing();
+      Thing.prototype = 1337;
+      expect(t).to.an.instanceof(Thing);
+    }, expectedError)
+
+    if (typeof Symbol !== 'undefined') {
+        err(function(){
+          expect(new Foo()).to.an.instanceof(Symbol());
+        }, "The instanceof assertion needs a constructor but symbol was given.");
+    }
+
     err(function(){
       expect(3).to.an.instanceof(Foo, 'blah');
     }, "blah: expected 3 to be an instance of Foo");

diff --git a/test/should.js b/test/should.js
@@ -416,6 +416,51 @@ describe('should', function() {
     function Foo(){}
     new Foo().should.be.an.instanceof(Foo);
 
+    err(function(){
+      new Foo().should.be.an.instanceof(1);
+    }, "The instanceof assertion needs a constructor but number was given.");
+
+    err(function(){
+      new Foo().should.be.an.instanceof('batman');
+    }, "The instanceof assertion needs a constructor but string was given.");
+
+    err(function(){
+      new Foo().should.be.an.instanceof({});
+    }, "The instanceof assertion needs a constructor but object was given.");
+
+    err(function(){
+      new Foo().should.be.an.instanceof(true);
+    }, "The instanceof assertion needs a constructor but boolean was given.");
+
+    err(function(){
+      new Foo().should.be.an.instanceof(null);
+    }, "The instanceof assertion needs a constructor but null was given.");
+
+    err(function(){
+      new Foo().should.be.an.instanceof(undefined);
+    }, "The instanceof assertion needs a constructor but undefined was given.");
+
+    // Different browsers may have different error messages
+    var expectedError;
+    try {
+      t instanceof Thing;
+    } catch (err) {
+      errMsg = '[object Object] instanceof function Thing(){} failed: ' + err.message + '.';
+    }
+
+    err(function(){
+      function Thing(){};
+      var t = new Thing();
+      Thing.prototype = 1337;
+      t.should.be.an.instanceof(Thing);
+    }, expectedError);
+
+    if (typeof Symbol !== 'undefined') {
+        err(function(){
+          new Foo().should.be.an.instanceof(Symbol());
+        }, "The instanceof assertion needs a constructor but symbol was given.");
+    }
+
     err(function(){
       (3).should.an.instanceof(Foo, 'blah');
     }, "blah: expected 3 to be an instance of Foo");