使用 hamcrest 检查列表是否包含特定顺序的类实例

Question

Hi I am writing a unit test where I need to assert that a list contains objects of multiple classes in a specific order. I want to do this using hamcrest.

Right now I am asserting it like -

assertThat(actual, hasItem(isA(A.class)));
assertThat(actual, hasItem(isA(B.class)));
assertThat(actual, hasItem(isA(C.class)));

Here I want to test that the items are in order A->B->C. I have tried writing it like -

assertThat(actual, contains(isA(A.class), isA(B.class), isA(C.class)));

but this is not supported, is there a way to achieve this with hamcrest matchers?

Answer 1

Use this method :

public static <E> Matcher<java.lang.Iterable<? extends E>> containsInRelativeOrder(Matcher<? super E>... itemMatchers)

From the docs:

Creates a matcher for Iterables that matches when a single pass over the examined Iterable yields a series of items, that each satisfying the corresponding matcher in the specified matchers, in the same relative order. For example: assertThat(Arrays.asList("a", "b", "c", "d", "e"), containsInRelativeOrder(equalTo("b"), equalTo("d")))

In your case, it could be like this:

assertThat(actual, containsInRelativeOrder(isA(A.class), isA(B.class), isA(C.class)));

Available since Hamcrest 2.0.0.0.