The necessary method is Mockito#verify:
public static <T> T verify(T mock,
VerificationMode mode)
mock is your mocked object and mode is the VerificationMode that describes how the mock should be verified. Possible modes are:
verify(mock, times(5)).someMethod("was called five times");
verify(mock, never()).someMethod("was never called");
verify(mock, atLeastOnce()).someMethod("was called at least once");
verify(mock, atLeast(2)).someMethod("was called at least twice");
verify(mock, atMost(3)).someMethod("was called at most 3 times");
verify(mock, atLeast(0)).someMethod("was called any number of times"); // useful with captors
verify(mock, only()).someMethod("no other method has been called on the mock");
You'll need these static imports from the Mockito class in order to use the verify method and these verification modes:
import static org.mockito.Mockito.atLeast;
import static org.mockito.Mockito.atLeastOnce;
import static org.mockito.Mockito.atMost;
import static org.mockito.Mockito.never;
import static org.mockito.Mockito.only;
import static org.mockito.Mockito.times;
import static org.mockito.Mockito.verify;
So in your case the correct syntax will be:
Mockito.verify(mock, times(4)).send()
This verifies that the method send was called 4 times on the mocked object. It will fail if it was called less or more than 4 times.
If you just want to check, if the method has been called once, then you don't need to pass a VerificationMode. A simple
verify(mock).someMethod("was called once");
would be enough. It internally uses verify(mock, times(1)).someMethod("was called once");.
It is possible to have multiple verification calls on the same mock to achieve a "between" verification. Mockito doesn't support something like this verify(mock, between(4,6)).someMethod("was called between 4 and 6 times");, but we can write
verify(mock, atLeast(4)).someMethod("was called at least four times ...");
verify(mock, atMost(6)).someMethod("... and not more than six times");
instead, to get the same behaviour. The bounds are included, so the test case is green when the method was called 4, 5 or 6 times.