This update means that we do select of first match.

To use this method, we need to make config, where user provided multiple patterns that overlap and we have import that can match several, and we select only best match.

So regression will not find anything, we just need to make bunch of unrealistic configs.

To catch a case, you can make this method as public, and trace all possible values to patterns and name to catch what we need. After that you simply take required patterns and put in Input.

@Kevin222004 , ping.
Please play with almost same groups.

@Kevin222004 , here is how to quicky play with this methods coverage - e0e1161

ones you kill it by pure unit test, you can convert it to Input based.

It is getting a long delay in this pr but I am trying to find test

Just a update on this pr I have found a pure ut which kill one mutation if (matcher.start() < bestPos) {

@Test
public void testPitest() throws Exception {
    Pattern[] patterns = new Pattern[6];

    patterns[0] = Pattern.compile("awt");
    patterns[5] = Pattern.compile("jarInputStream");
    patterns[4] = Pattern.compile(".util");
    patterns[3] = Pattern.compile(".jar.");
    patterns[2] = Pattern.compile(".util.");
    patterns[1] = Pattern.compile("jar");

    assertWithMessage("")
            .that(ImportOrderCheck.getGroupNumber(patterns, "java.util.jar.JarInputStream"))
            .isEqualTo(4);
}

I am trying to make this input base and also for other mutation trying to find test

we missed a fact that we treat provided packages as full name from the beginning,

so we can not use .util or awt , all patterns must have full name from the beginning. So it meant that getGroupNumber should be aware of this, so finding most early bestPos is nonsense at line if (matcher.start() < bestPos) {.

ok, we can use regexp, but we have to use / around values to make it treated as-is - https://checkstyle.org/checks/imports/importorder.html#Properties