How to ensure a string has a substring exactly n times?

Question

I want to check whether a String contains a certain substring n times. I know I can do:

Assertions.assertThat(myString).contains("xyz");

Or even Assertions.assertThat(myString).containsOnlyOnce("xyz");

But how can I ensure this for n times?

I tried something like:

Assertions.assertThat(myString).areExactly(n, myString.contains("xyz")); but sadly this is not compilable.

Any ideas?

Answer 1

You are probably looking for StringUtils.countMatches

Counts the number of occurrences of one String in another

Answer 2

You can have the regex like this which test String "myString" has SubString "xyz" n times.

Assertions.assertThat(myString).containsPattern("(xyz.*?){n}");

You can replace n with the count of substring you want to test.