[FIXED] How to use EqualsWithDelta of junit

Issue

versions:

<dependency>
  <groupId>org.mockito</groupId>
  <artifactId>mockito-all</artifactId>
  <version>1.9.5</version>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.junit.jupiter</groupId>
  <artifactId>junit-jupiter-api</artifactId>
  <version>5.2.0</version>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.junit.jupiter</groupId>
  <artifactId>junit-jupiter-engine</artifactId>
  <version>5.2.0</version>
  <scope>test</scope>
</dependency>

I am trying to use EqualsWithDelta like below, which is not working, however in similar way Equals works, is there something I am missing in my implementation:

import org.junit.Assert
import org.mockito.internal.matchers.{Equals, EqualsWithDelta}
val testVarLong = testFuncReturningLong()
val testVarStr = testFuncReturningString()
Assert.assertThat( System.currentTimeMillis(), new EqualsWithDelta(testVarLong, 1000L))      <-- This does not  work
Assert.assertThat( "myTest", new Equals(testVarStr))   <-- This works

Following is compile time error I get:

Error:(82, 52) type mismatch;
 found   : org.mockito.internal.matchers.EqualsWithDelta
 required: org.hamcrest.Matcher[_ >: Any]
Note: Number <: Any (and org.mockito.internal.matchers.EqualsWithDelta <: org.mockito.ArgumentMatcher[Number]), but Java-defined trait Matcher is invariant in type T.
You may wish to investigate a wildcard type such as `_ <: Any`. (SLS 3.2.10)
    Assert.assertThat( System.currentTimeMillis(), new EqualsWithDelta(testVarLong, 1000L))

Solution

new EqualsWithDelta(...) is a Matcher[Number]. System.currentTimeMillis() is a Long. Assert.assertThat signature is assertThat(T actual, org.hamcrest.Matcher<T> matcher). So EqualsWithDelta must be a subtype of Matcher<T> and Long must be a subtype of T. The first implies T must be Number, but Long isn't a subtype of Number. So type inference reports such a T doesn't exist.

However, if you ask for Number explicitly in one of two ways:

assertThat[Number](System.currentTimeMillis(), new EqualsWithDelta(testVarLong, 1000L))

assertThat(System.currentTimeMillis(): Number, new EqualsWithDelta(testVarLong, 1000L))

this will trigger the implicit conversion from Long to java.lang.Long as a subtype of Number.

Answered By - Alexey Romanov