Goals

Tutorial / blog posts:

Usage

usingstaticNExpect.Expectations;

// simple equality checksExpect(1).To.Equal(1);Expect(true).To.Not.Be.False();// alt. grammarExpect(null).To.Be.Null();// - with negation, order doesn't matterExpect("moo").Not.To.Equal("cow");Expect("moo").To.Not.Equal("cow");Expect(true).Not.To.Be.False();Expect(false).To.Not.Be.True();// exceptionsExpect(()=>{}).Not.To.Throw();Expect(()=>{thrownewArgumentException("moo","moo cow");}).To.Throw<ArgumentException>().With.Message.Containing("moo").And.("cow");// smarter string tests, with fluencyExpect(someString).To.Contain("moo").And("cow");Expect("moo, said the cow").To.Start.With("moo").And.Contain("said").Then("the").And.End.With("cow");// collection testsExpect(someCollection).To.Contain.Exactly(2).Matched.By(item=>item.IsWhatWeWant());Expect(someCollection).To.Contain.Only(1).Deep.Equal.To(new{id=42,name="Douglas"});Expect(someFlags).To.Contain.At.Least(3).Equal.To(true);Expect(new[]{1,2,3}).To.Be.Ordered.Ascending();Expect(new[]{"c","b","a"}).To.Be.Ordered.Descending();// type testingExpect(someObject).To.Be.An.Instance.Of<Cow>();// deep and intersection equality testingvarperson=new{id=1,name="bob"};Expect(person).To.Deep.Equal(new{id=1,name="bob"});Expect(person).To.Intersection.Equal(new{name="bob"});// deep equality testing with excluded propsExpect(person).To.Deep.Equal(new{id=1,name="sarah"},exclude:["name"]);// orExpect(person).Omitting("name").To.Deep.Equal(new{id=1,name="sipho"});

Extending

usingNExpect.MatcherLogic

publicstaticclassMyMatchers{publicstaticvoidFive(thisIBe<int>continuation){continuation.AddMatcher(actual=>{varpassed=actual==5;varmessage=passed?$"Expected{actual} not to be 5":$"Expected{actual} to be 5";returnnewMatcherResult(passed,message);});}}

// somewhere else...[Test]publicvoidFifteenDividedByThree_ShouldEqual_Five(){varresult=15/3;Expect(result).To.Be.Five();}// Yes, yes, simple example is simple.

// beforevarcow=animalFactory.MakeCow();varbeetle=animalFactory.MakeBeetle();// animal factory should make a Jersey cowExpect(cow.Classification).To.Equal("Mammal");Expect(cow.Legs).To.Equal(4);Expect(cow.HasTail).To.Be.True();Expect(cow.HasHorns).To.Be.True();Expect(cow.HasSpots).To.Be.True();// Animal factory should make a rhinoceros beetleExpect(beetle.Classification).To.Equal("Insect");Expect(beetle.Legs).To.Equal(6);Expect(beetle.HasTail).To.Be.False();Expect(beetle.HasHorns).To.Be.True();Expect(beetle.HasSpots).To.Be.False();

// aftervarcow=animalFactory.MakeJerseyCow();varbeetle=animalFactory.MakeRhinocerosBeetle();Expect(cow).To.Be.A.JerseyCow();Expect(beetle).To.Be.A.RhinocerosBeetle();// elsewhere:publicstaticclassAnimalMatchers{// the IMore<T> interface allows fluent chaining of expectations//  eg://  Expect(cow).To.Be.A.JerseyCow()//     .And//     .Not.To.Be.A.FrieslandCow();publicstaticIMore<Animal>JerseyCow(thisIA<Animal>a){returna.Compose(actual=>{Expect(cow.Classification).To.Equal("Mammal");Expect(cow.Legs).To.Equal(4);Expect(cow.HasTail).To.Be.True();Expect(cow.HasHorns).To.Be.True();Expect(cow.HasSpots).To.Be.True();});}publicstaticIMore<Animal>RhinocerosBeetle(thisIA<Animal>a){returna.Compose(actual=>{Expect(beetle.Classification).To.Equal("Insect");Expect(beetle.Legs).To.Equal(6);Expect(beetle.HasTail).To.Be.False();Expect(beetle.HasHorns).To.Be.True();Expect(beetle.HasSpots).To.Be.False();});}}

usingNExpect.Implementations;usingNExpect.MatcherLogic;usingNExpect;usingstaticNExpect.Expectations;publicstaticclassAnimalMatchers{publicstaticIMore<Animal>JerseyCow(thisIA<Animal>a){returna.Compose(actual=>{// the Stringify extension method, available on all types,// comes from NExpect.Implementation.MessageHelpers and// produces a string representation of the object it's// operating on which is similar to JSON, so it's easier// to read what the object wasvarcustomMessage=$"Expected{actual.Stringify()} to be a cow";Expect(cow.Classification).To.Equal("Mammal",customMessage);Expect(cow.Legs).To.Equal(4,customMessage);Expect(cow.HasTail).To.Be.True(customMessage);Expect(cow.HasHorns).To.Be.True(customMessage);Expect(cow.HasSpots).To.Be.True(customMessage);});}publicstaticIMore<Animal>RhinocerosBeetle(thisIA<Animal>a){returna.Compose(actual=>{// we can use a generator func to delay generation of the message//  which is especially helpful if message generation is expensive//  and we'd only like to spend that cpu time on a failureFunc<string>customMessageGenerator=()=>$"Expected{actual.Stringify()} to be a cow";Expect(beetle.Classification).To.Equal("Insect",customMessageGenerator);Expect(beetle.Legs).To.Equal(6,customMessageGenerator);Expect(beetle.HasTail).To.Be.False(customMessageGenerator);Expect(beetle.HasHorns).To.Be.True(customMessageGenerator);Expect(beetle.HasSpots).To.Be.False(customMessageGenerator);});}}