Jasmine JavaScript Testing - toBe vs toEqual

Question

Let s say I have the following   var myNumber   5  expect myNumber  toBe 5   expect myNumber  toEqual 5     Both of the above tests will pass  Is there a difference between toBe   and toEqual   when it comes to evaluating numbers  If so  when I should use one and not the other

User · Answer

Thought someone might like explanation by (annotated) example:

Below, if my deepClone() function does its job right, the test (as described in the 'it()' call) will succeed:

describe('deepClone() array copy', ()=>{
    let source:any = {}
    let clone:any = source
    beforeAll(()=>{
        source.a = [1,'string literal',{x:10, obj:{y:4}}]
        clone = Utils.deepClone(source) // THE CLONING ACT TO BE TESTED - lets see it it does it right.
    })
    it('should create a clone which has unique identity, but equal values as the source object',()=>{
        expect(source !== clone).toBe(true) // If we have different object instances...
        expect(source).not.toBe(clone) // <= synonymous to the above. Will fail if: you remove the '.not', and if: the two being compared are indeed different objects.
        expect(source).toEqual(clone) // ...that hold same values, all tests will succeed.
    })
})

Of course this is not a complete test suite for my deepClone(), as I haven't tested here if the object literal in the array (and the one nested therein) also have distinct identity but same values.

User · Answer

toBe   versus toEqual    toEqual   checks equivalence  toBe    on the other hand  makes sure that they re the exact same object  I would say use toBe   when comparing values  and toEqual   when comparing objects  When comparing primitive types  toEqual   and toBe   will yield the same result  When comparing objects  toBe   is a stricter comparison  and if it is not the exact same object in memory this will return false  So unless you want to make sure it s the exact same object in memory  use toEqual   for comparing objects  Check this link out for more info   http   evanhahn com how-do-i-jasmine  Now when looking at the difference between toBe   and toEqual   when it comes to numbers  there shouldn t be any difference so long as your comparison is correct  5 will always be equivalent to 5  A nice place to play around with this to see different outcomes is here Update An easy way to look at toBe   and toEqual   is to understand what exactly they do in JavaScript  According to Jasmine API  found here   toEqual   works for simple literals and variables  and should work for objects toBe   compares with      Essentially what that is saying is toEqual   and toBe   are similar Javascripts     operator except toBe   is also checking to make sure it is the exact same object  in that for the example below objectOne     objectTwo   returns false as well  However  toEqual   will return true in that situation  Now  you can at least understand why when given  var objectOne         propertyOne  str      propertyTwo  num        var objectTwo         propertyOne  str      propertyTwo  num        expect objectOne  toBe objectTwo     returns false That is because  as stated in this answer to a different  but similar question  the     operator actually means that both operands reference the same object  or in case of value types  have the same value

User · Answer

toEqual   compares values if Primitive or contents if Objects  toBe   compares references   Following code   suite should be self explanatory    describe  Understanding toBe vs toEqual        gt      let obj1  obj2  obj3     beforeEach      gt        obj1           a  1        b   some string         c  true             obj2           a  1        b   some string         c  true             obj3   obj1           afterEach      gt        obj1   null      obj2   null      obj3   null           it  Obj1     Obj2        gt        expect obj1  toEqual obj2            it  Obj1     Obj3        gt        expect obj1  toEqual obj3            it  Obj1    gt  Obj2        gt        expect obj1  not toBe obj2            it  Obj1    gt  Obj3        gt        expect obj1  toBe obj3

User · Answer

I think toEqual is checking deep equal  toBe is the same reference of 2 variable    it  test me        gt        expect            toEqual false     true     expect           toEqual false     true      expect     toEqual         true    deep check     expect     toBe         false

User · Answer

For primitive types  e g  numbers  booleans  strings  etc    there is no difference between toBe and toEqual  either one will work for 5  true  or  quot the cake is a lie quot   To understand the difference between toBe and toEqual  let s imagine three objects  var a     bar   baz         b     foo  a        c     foo  a     Using a strict comparison        some things are  quot the same quot    gt  b foo bar     c foo bar true   gt  b foo bar     a bar true   gt  c foo     b foo true  But some things  even though they are  quot equal quot   are not  quot the same quot   since they represent objects that live in different locations in memory   gt  b     c false  Jasmine s toBe matcher is nothing more than a wrapper for a strict equality comparison expect c foo  toBe b foo   is the same thing as expect c foo     b foo  toBe true   Don t just take my word for it  see the source code for toBe  But b and c represent functionally equivalent objects  they both look like   foo    bar   baz       Wouldn t it be great if we could say that b and c are  quot equal quot  even if they don t represent the same object  Enter toEqual  which checks  quot deep equality quot   i e  does a recursive search through the objects to determine whether the values for their keys are equivalent   Both of the following tests will pass  expect b  not toBe c   expect b  toEqual c    Hope that helps clarify some things

User · Answer

Looking at the Jasmine source code sheds more light on the issue    toBe is very simple and just uses the identity strict equality operator          function actual  expected        return         pass  actual     expected              toEqual  on the other hand  is nearly 150 lines long and has special handling for built in objects like String  Number  Boolean  Date  Error  Element and RegExp  For other objects it recursively compares properties   This is very different from the behavior of the equality operator      For example   var simpleObject    foo   bar    expect simpleObject  toEqual  foo   bar       true simpleObject     foo   bar      false  var castableObject    toString  function   return  bar     expect castableObject  toEqual  bar      false castableObject     bar     true

User · Answer

To quote the jasmine github project      expect x  toEqual y   compares objects or primitives x and y and   passes if they are equivalent      expect x  toBe y   compares objects or primitives x and y and passes   if they are the same object

[javascript] Jasmine JavaScript Testing - toBe vs toEqual

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