replace occurrence in Java with JUnit

I will write a more detailed post about JUnit later on. But this is a good start to find out testing replacing occurrence in Java 🙂

Assuming the utility method is as follows:

public class Strings {

    public static String replaceOccurence(String str, String search, String replace) {
        StringBuffer buffer = new StringBuffer(str);
        for (int i = 0; i < str.length() - search.length() + 1; i++) {
            if (str.substring(i, i + search.length()).equals(search)) {
                buffer.replace(i, i + search.length(), replace);
            }
        }
        return buffer.toString();
    }
}

In the following codeblock, the last method would be a good start to check:

public class TestStringManipulation extends TestCase {

	public void testReplaceOnce() {
		String input = "aaa bbb ccc";
		String expected = "ddd bbb ccc";

		String output = Strings.replaceOccurence(input, "aaa", "ddd");

		assertEquals(expected, output);
	}

	public void testReplaceTwice() {
		String input = "aaa bbb ccc aaa";
		String expected = "ddd bbb ccc ddd";

		String output = Strings.replaceOccurence(input, "aaa", "ddd");

		assertEquals(expected, output);
	}

	public void testReplaceMultiple() {
		String input = "ab ab ac ad ab ac ad ab ab ad";
		String expected = "ba ba ac ad ba ac ad ba ba ad";

		String output = Strings.replaceOccurence(input, "ab", "ba");

		assertEquals(expected, output);
	}

	public void testMatchNotFound() {
		String input = "ab ab ac ad ab ac ad ab ab ad";
		String expected = "ab ab ac ad ab ac ad ab ab ad";

		String output = Strings.replaceOccurence(input, "zz", "ba");

		assertEquals(expected, output);
	}

	public void testReplaceSingleCharWithMultiChar() {
		String input = "abcdefgabcdefgabcdefg";
		String expected = "abcdefghijkabcdefghijkabcdefghijk";

		String output = Strings.replaceOccurence(input, "g", "ghijk");

		assertEquals(expected, output);
	}
}