Jasmine文档（二）

前言

这是翻译的Jasmine文档第二篇，第一篇文章的地址为：
Jasmine文档（一）

Spies（间谍）

Jasmine有称为间谍（spies）的测试双重功能。一个spy可以监测任何函数的调用和参数的调用痕迹。Spy只能存在于定义它的describe()和it()代码块内，而在每一个spec结束后将被移除。（这个语法在Jasmine2.0才改变的）
有几个特别的Matchers于spy相互作用：
toHaveBeenCalled()：在spy被调用是返回true；
toHaveBeenCalledTimes()：在spy调用指定次数的时候会通过测试；
toHaveBeenCalledWith()：如果匹配任一调用的参数列表，则返回true。
例子：

describe("A spy", function() {  var foo, bar = null;  beforeEach(function() {    foo = {      setBar: function(value) {        bar = value;      }    };    spyOn(foo, 'setBar');//使用spyOn()来声明spy    foo.setBar(123);    foo.setBar(456, 'another param');  });  it("tracks that the spy was called", function() {    //测试spy是否调用    expect(foo.setBar).toHaveBeenCalled();  });  it("tracks that the spy was called x times", function() {    //测试spy是否调用两次    expect(foo.setBar).toHaveBeenCalledTimes(2);  });  it("tracks all the arguments of its calls", function() {    //测试spy调用时的参数列表是否匹配    expect(foo.setBar).toHaveBeenCalledWith(123);    expect(foo.setBar).toHaveBeenCalledWith(456, 'another param');  });  it("stops all execution on a function", function() {    //Spy的调用并不会影响真实的值，所以bar仍然是null。    expect(bar).toBeNull();  });});

and.callThrough

Spy通过链式调用and.callThrough，除了追踪所有的调用之外，它将委托实际的实现值。例如：

describe("A spy, when configured to call through", function() {  var foo, bar, fetchedBar;  beforeEach(function() {    foo = {      setBar: function(value) {        bar = value;      },      getBar: function() {        return bar;      }    };    spyOn(foo, 'getBar').and.callThrough();//定义spy并且链式调用and.callThrough()    foo.setBar(123);    fetchedBar = foo.getBar();//调用spy  });  it("tracks that the spy was called", function() {    expect(foo.getBar).toHaveBeenCalled();  });  it("should not affect other functions", function() {    expect(bar).toEqual(123);  });  it("when called returns the requested value", function() {    expect(fetchedBar).toEqual(123);//fetchedBar为函数实际返回的值。  });});

将上述代码对比于一下代码：

describe("A spy, when configured to call through", function() {  var foo, bar, fetchedBar;  beforeEach(function() {    foo = {      setBar: function(value) {        bar = value;      },      getBar: function() {        return bar;      }    };    spyOn(foo, 'getBar');//不再链式调用and.callThrough()    foo.setBar(123);    fetchedBar = foo.getBar();  });  it("tracks that the spy was called", function() {    expect(foo.getBar).toHaveBeenCalled();  });  it("should not affect other functions", function() {    expect(bar).toEqual(123);  });  it("when called returns the requested value", function() {    expect(fetchedBar).toBeUndefined();//此时的fetchedBar不再是函数返回的实际值，而是undefined  });});

and.returnValue

Spy通过链式调用and.returnValue，所有调用spy的都将返回一个指定值。例如：

describe("A spy, when configured to fake a return value", function() {  var foo, bar, fetchedBar;  beforeEach(function() {    foo = {      setBar: function(value) {        bar = value;      },      getBar: function() {        return bar;      }    };    spyOn(foo, "getBar").and.returnValue(745);//指定返回745    foo.setBar(123);    fetchedBar = foo.getBar();  });  it("tracks that the spy was called", function() {    expect(foo.getBar).toHaveBeenCalled();  });  it("should not affect other functions", function() {    expect(bar).toEqual(123);  });  it("when called returns the requested value", function() {    expect(fetchedBar).toEqual(745);//返回特定值为745  });});

and.returnValues

Spy通过链式调用and.returnValues，所有调用该spy的函数都将按顺序返回一些特定的值，直到返回值队列的最后，这之后的所有调用将返回undefined。例如：

describe("A spy, when configured to fake a series of return values", function() {  var foo, bar;  beforeEach(function() {    foo = {      setBar: function(value) {        bar = value;      },      getBar: function() {        return bar;      }    };    spyOn(foo, "getBar").and.returnValues("fetched first", "fetched second");    foo.setBar(123);  });  it("tracks that the spy was called", function() {    foo.getBar(123);    expect(foo.getBar).toHaveBeenCalled();  });  it("should not affect other functions", function() {    expect(bar).toEqual(123);  });  it("when called multiple times returns the requested values in order", function() {    expect(foo.getBar()).toEqual("fetched first");//第一次调用，返回队列的第一个值    expect(foo.getBar()).toEqual("fetched second");//第二次调用，返回队列的第二个值    expect(foo.getBar()).toBeUndefined();//之后的调用都将返回undefined  });});

and.callFake

Spy通过调用and.callFake，所有调用该spy的都将调用其提供的函数，例如：

describe("A spy, when configured with an alternate implementation", function() {  var foo, bar, fetchedBar;  beforeEach(function() {    foo = {      setBar: function(value) {        bar = value;      },      getBar: function() {        return bar;      }    };    spyOn(foo, "getBar").and.callFake(function() {      return 1001;    });    foo.setBar(123);    fetchedBar = foo.getBar();  });  it("tracks that the spy was called", function() {    expect(foo.getBar).toHaveBeenCalled();  });  it("should not affect other functions", function() {    expect(bar).toEqual(123);  });  it("when called returns the requested value", function() {    expect(fetchedBar).toEqual(1001);  });});

and.throwError

Spy链式调用and.throwError，调用该spy的将以一个错误的形式抛出特殊返回值，例如：

describe("A spy, when configured to throw an error", function() {  var foo, bar;  beforeEach(function() {    foo = {      setBar: function(value) {        bar = value;      }    };    spyOn(foo, "setBar").and.throwError("quux");  });  it("throws the value", function() {    expect(function() {      foo.setBar(123)    }).toThrowError("quux");  });});

and.stub

Spy链式调用以上某一个策略后，可以调用and.stub随时返回之前保存的原始数据，而不进行修改。例如：

describe("A spy", function() {  var foo, bar = null;  beforeEach(function() {    foo = {      setBar: function(value) {        bar = value;      }    };    spyOn(foo, 'setBar').and.callThrough();  });  it("can call through and then stub in the same spec", function() {    foo.setBar(123);//调用策略and.callThrough()所定义的spy    expect(bar).toEqual(123);//bar数值被修改为123    foo.setBar.and.stub();//调用and.stub()    bar = null;    foo.setBar(123);//调用spy    expect(bar).toBe(null);//bar不再返回and.callThrough()的实现值  });});

其他跟踪属性

任何调用spy的都将被追踪，并且暴露在calls的属性中。
calls属性有：
1. .calls.any()：一次都没调用时返回false，一旦调用至少一次就返回true；
2. .calls.count()：返回spy调用的次数
3. .calls.argsFor(index)：返回第index+1次调用时传递的参数，index从0开始；
4. .calls.allArgs()：以数组的形式返回调用时传递的所有参数；
5. .calls.all()：以对象形式返回上下文（this），以及所有传递的参数；
6. .calls.mostRecent()：以对象形式返回最近一次调用的上下文（this），以及传递的参数；
7. .calls.first()：以对象形式返回第一次调用的上下文（this），以及传递的参数；（当检查.calls.all()，.calls.mostRecent()，.calls.first()返回的对象时，.object属性指向的是调用该spy的this对象）
8. .calls.reset()：清空spy的所有追踪。
上述属性值，例子如下：

describe("A spy", function() {  var foo, bar = null;  beforeEach(function() {    foo = {      setBar: function(value) {        bar = value;      }    };    spyOn(foo, 'setBar');  });    it("tracks if it was called at all", function() {    expect(foo.setBar.calls.any()).toEqual(false);    foo.setBar();    expect(foo.setBar.calls.any()).toEqual(true);  });    it("tracks the number of times it was called", function() {    expect(foo.setBar.calls.count()).toEqual(0);    foo.setBar();    foo.setBar();    expect(foo.setBar.calls.count()).toEqual(2);  });    it("tracks the arguments of each call", function() {    foo.setBar(123);    foo.setBar(456, "baz");    expect(foo.setBar.calls.argsFor(0)).toEqual([123]);    expect(foo.setBar.calls.argsFor(1)).toEqual([456, "baz"]);  });    it("tracks the arguments of all calls", function() {    foo.setBar(123);    foo.setBar(456, "baz");    expect(foo.setBar.calls.allArgs()).toEqual([[123],[456, "baz"]]);  });    it("can provide the context and arguments to all calls", function() {    foo.setBar(123);    expect(foo.setBar.calls.all()).toEqual([{object: foo, args: [123], returnValue: undefined}]);  });    it("has a shortcut to the most recent call", function() {    foo.setBar(123);    foo.setBar(456, "baz");    expect(foo.setBar.calls.mostRecent()).toEqual({object: foo, args: [456, "baz"], returnValue: undefined});  });    it("has a shortcut to the first call", function() {    foo.setBar(123);    foo.setBar(456, "baz");    expect(foo.setBar.calls.first()).toEqual({object: foo, args: [123], returnValue: undefined});  });    it("tracks the context", function() {    var spy = jasmine.createSpy('spy');    var baz = {      fn: spy    };    var quux = {      fn: spy    };    baz.fn(123);    quux.fn(456);    //当检查.calls.all()，.calls.mostRecent()，.calls.first()返回的对象时，.object属性指向的是调用该spy的this对象    expect(spy.calls.first().object).toBe(baz);    expect(spy.calls.mostRecent().object).toBe(quux);  });    it("can be reset", function() {    foo.setBar(123);    foo.setBar(456, "baz");    expect(foo.setBar.calls.any()).toBe(true);    foo.setBar.calls.reset();    expect(foo.setBar.calls.any()).toBe(false);  });});

Spies：createSpy

如果没有一个函数可以spyOn，jasmine.createSpy可以创建一个“空白”的spy。该spy会像其他间谍一样追踪调用，函数等等，但是在其之后并不会有实际实现的返回值。Spies是JavaScript对象，可以这样使用：

describe("A spy, when created manually", function() {  var whatAmI;  beforeEach(function() {    whatAmI = jasmine.createSpy('whatAmI');    whatAmI("I", "am", "a", "spy");  });  it("is named, which helps in error reporting", function() {    expect(whatAmI.and.identity()).toEqual('whatAmI');  });  it("tracks that the spy was called", function() {    expect(whatAmI).toHaveBeenCalled();  });  it("tracks its number of calls", function() {    expect(whatAmI.calls.count()).toEqual(1);  });  it("tracks all the arguments of its calls", function() {    expect(whatAmI).toHaveBeenCalledWith("I", "am", "a", "spy");  });  it("allows access to the most recent call", function() {    expect(whatAmI.calls.mostRecent().args[0]).toEqual("I");  });});

Spies：createSpyObj

为了创建一个多重spies的模拟，使用jasmine.createSpyObj()并传递一个字符串的数组，将会返回一个对象，对象包括每个字符串绑定的spy属性。例如：

describe("Multiple spies, when created manually", function() {  var tape;  beforeEach(function() {    tape = jasmine.createSpyObj('tape', ['play', 'pause', 'stop', 'rewind']);    tape.play();    tape.pause();    tape.rewind(0);  });  it("creates spies for each requested function", function() {    expect(tape.play).toBeDefined();    expect(tape.pause).toBeDefined();    expect(tape.stop).toBeDefined();    expect(tape.rewind).toBeDefined();  });  it("tracks that the spies were called", function() {    expect(tape.play).toHaveBeenCalled();    expect(tape.pause).toHaveBeenCalled();    expect(tape.rewind).toHaveBeenCalled();    expect(tape.stop).not.toHaveBeenCalled();  });  it("tracks all the arguments of its calls", function() {    expect(tape.rewind).toHaveBeenCalledWith(0);  });});

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有兴趣的同学可以查看下一篇文章：
Jasmine文档（三）