toBe true vs toBeTruthy vs toBeTrue

Question

What is the difference between expect something  toBe true   expect something  toBeTruthy   and expect something  toBeTrue     Note that toBeTrue   is a custom matcher introduced in jasmine-matchers among other useful and handy matchers like toHaveMethod   or toBeArrayOfStrings       The question is meant to be generic  but  as a real-world example  I m testing that an element is displayed in protractor  Which matcher should I use in this case   expect elm isDisplayed    toBe true   expect elm isDisplayed    toBeTruthy    expect elm isDisplayed    toBeTrue

User · Answer

In javascript there are trues and truthys. When something is true it is obviously true or false. When something is truthy it may or may not be a boolean, but the "cast" value of is a boolean.

Examples.

true == true; // (true) true
1 == true; // (true) truthy
"hello" == true;  // (true) truthy
[1, 2, 3] == true; // (true) truthy
[] == false; // (true) truthy
false == false; // (true) true
0 == false; // (true) truthy
"" == false; // (true) truthy
undefined == false; // (true) truthy
null == false; // (true) truthy

This can make things simpler if you want to check if a string is set or an array has any values.

var users = [];

if(users) {
  // this array is populated. do something with the array
}

var name = "";

if(!name) {
  // you forgot to enter your name!
}

And as stated. expect(something).toBe(true) and expect(something).toBeTrue() is the same. But expect(something).toBeTruthy() is not the same as either of those.

User · Answer

What I do when I wonder something like the question asked here is go to the source   toBe    expect   toBe   is defined as   function toBe       return       compare  function actual  expected          return           pass  actual     expected                         It performs its test with     which means that when used as expect foo  toBe true   it will pass only if foo actually has the value true  Truthy values won t make the test pass   toBeTruthy    expect   toBeTruthy   is defined as   function toBeTruthy       return       compare  function actual          return           pass    actual                         Type coercion  A value is truthy if the coercion of this value to a boolean yields the value true  The operation    tests for truthiness by coercing the value passed to expect to a boolean  Note that contrarily to what the currently accepted answer implies     true is not a correct test for truthiness  You ll get funny things like    gt   hello     true false  gt        true false  gt        true false  gt   1  2  3     true false   Whereas using    yields    gt     hello  true  gt       false  gt     1  2  3  true  gt        true    Yes  empty or not  an array is truthy    toBeTrue    expect   toBeTrue   is part of Jasmine-Matchers  which is registered on npm as jasmine-expect after a later project registered jasmine-matchers first     expect   toBeTrue   is defined as   function toBeTrue actual      return actual     true        is actual   Boolean    amp  amp      actual valueOf        The difference with expect   toBeTrue   and expect   toBe true  is that expect   toBeTrue   tests whether it is dealing with a Boolean object  expect new Boolean true   toBe true  would fail whereas expect new Boolean true   toBeTrue   would pass  This is because of this funny thing    gt  new Boolean true      true false  gt  new Boolean true      false false   At least it is truthy    gt    new Boolean true  true   Which is best suited for use with elem isDisplayed     Ultimately Protractor hands off this request to Selenium  The documentation states that the value produced by  isDisplayed   is a promise that resolves to a boolean  I would take it at face value and use  toBeTrue   or  toBe true   If I found a case where the implementation returns truthy falsy values  I would file a bug report

User · Answer

Disclamer  This is just a wild guess   I know everybody loves an easy-to-read list    toBe  lt value gt   - The returned value is the same as  lt value gt  toBeTrue   - Checks if the returned value is true toBeTruthy   - Check if the value  when cast to a boolean  will be a truthy value  Truthy values are all values that aren t 0      empty string   false  null  NaN  undefined or     empty array       Notice that when you run       it returns true  but when you run       false it also returns true  It depends on how it is implemented  In other words                    false      On your example  toBe true  and toBeTrue   will yield the same results

User · Answer

As you read through the examples below  just keep in mind this difference true     true    true  quot string quot      true    false 1     true    false        true    false  But Boolean  quot string quot       true    true Boolean 1      true    true Boolean         true    true  1  expect statement  toBe true  Assertion passes when the statement passed to expect   evaluates to true expect true  toBe true     pass expect  quot 123 quot       quot 123 quot   toBe true     pass  In all other cases cases it would fail expect  quot string quot   toBe true     fail expect 1  toBe true      fail expect     toBe true     fail  Even though all of these statements would evaluate to true when doing Boolean    So you can think of it as  strict  comparison 2  expect statement  toBeTrue   This one does exactly the same type of comparison as  toBe true   but was introduced in Jasmine recently in version 3 5 0 on Sep 20  2019 3  expect statement  toBeTruthy   toBeTruthy on the other hand  evaluates the output of the statement into boolean first and then does comparison expect false  toBeTruthy      fail expect null  toBeTruthy      fail expect undefined  toBeTruthy      fail expect NaN  toBeTruthy      fail expect  quot  quot   toBeTruthy      fail expect 0  toBeTruthy      fail  And IN ALL OTHER CASES it would pass  for example expect  quot string quot   toBeTruthy      pass expect 1  toBeTruthy      pass expect     toBeTruthy      pass

User · Answer

There are a lot many good answers out there  i just wanted to add a scenario where the usage of these expectations might be helpful  Using element all xxx   if i need to check if all elements are displayed at a single run  i can perform -  expect element all xxx  isDisplayed    toBeTruthy      Expectation passes expect element all xxx  isDisplayed    toBe true     Expectation fails expect element all xxx  isDisplayed    toBeTrue      Expectation fails   Reason being  all   returns an array of values and so all kinds of expectations getText  isPresent  etc     can be performed with toBeTruthy   when  all   comes into picture  Hope this helps

[javascript] toBe(true) vs toBeTruthy() vs toBeTrue()

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