JUnit 单元测试示例：FileReader 类测试用例

import static org.junit.Assert.; import org.junit.Test; import java.io.;

public class TestFileReader {

@Test
public void testEmptyString() {
    FileReader fr = new FileReader();
    BufferedReader br = fr.read('');
    assertNotNull(br);
}

@Test
public void testNonexistentFile() {
    FileReader fr = new FileReader();
    BufferedReader br = fr.read('notExist.txt');
    assertNull(br);
}

@Test
public void testExistingFile() {
    FileReader fr = new FileReader();
    BufferedReader br = fr.read('test.txt');
    assertNotNull(br);
}

@Test
public void testEmptyBufferedReader() {
    FileReader fr = new FileReader();
    BufferedReader br = new BufferedReader(new StringReader(''));
    assertNull(fr.read(br));
}

@Test
public void testNonemptyBufferedReader() {
    FileReader fr = new FileReader();
    BufferedReader br = new BufferedReader(new StringReader('a'));
    assertEquals(97, fr.read(br));
}

@Test
public void testIllegalCharacter() {
    FileReader fr = new FileReader();
    BufferedReader br = new BufferedReader(new StringReader('@'));
    assertNull(fr.read(br));
}

@Test
public void testSpecialCharacter() {
    FileReader fr = new FileReader();
    BufferedReader br = new BufferedReader(new StringReader('#'));
    assertEquals(35, fr.read(br));
}

@Test
public void testKeyword() {
    FileReader fr = new FileReader();
    BufferedReader br = new BufferedReader(new StringReader('while'));
    assertEquals('while', fr.read(br));
}

@Test
public void testIdentifier() {
    FileReader fr = new FileReader();
    BufferedReader br = new BufferedReader(new StringReader('var1'));
    assertEquals('var1', fr.read(br));
}

@Test
public void testNumericConstant() {
    FileReader fr = new FileReader();
    BufferedReader br = new BufferedReader(new StringReader('123'));
    assertEquals('123', fr.read(br));
}

@Test
public void testStringConstant() {
    FileReader fr = new FileReader();
    BufferedReader br = new BufferedReader(new StringReader(''hello''));
    assertEquals(''hello'', fr.read(br));
}

@Test
public void testCharacterConstant() {
    FileReader fr = new FileReader();
    BufferedReader br = new BufferedReader(new StringReader(''a''));
    assertEquals(''a'', fr.read(br));
}

@Test
public void testComment() {
    FileReader fr = new FileReader();
    BufferedReader br = new BufferedReader(new StringReader('// This is a comment'));
    assertEquals('// This is a comment', fr.read(br));
}

}