如何编写JUnit测试用例来查找流中的第一个非重复字符？

import org.junit.Test;
import java.io.ByteArrayInputStream;
import java.io.InputStream;

import static org.junit.Assert.assertEquals;

public class FirstNonRepeatedCharTest {

    @Test
    public void testFindFirstNonRepeatedChar() {
        String input = "aabbccddeeffgghhii";
        InputStream inputStream = new ByteArrayInputStream(input.getBytes());
        char result = FirstNonRepeatedChar.findFirstNonRepeatedChar(inputStream);
        assertEquals('g', result);
    }
}