### Question:
Frame { @Override public String toString() { StringBuilder builder = new StringBuilder(); builder = builder.append("\tat ").append(className).append('.').append(methodName).append('('); if(isNative()) { builder = builder.append("Native Method"); } else if(isUnknown()) { builder = builder.append("Unknown Source"); } else { builder = builder.append(fileName).append(':').append(lineNumber); } builder = builder.append(')'); return builder.toString(); } Frame(String className, String methodName);  Frame(String className, String methodName, String fileName, int lineNumber); String getClassName(); void setClassName(String className); String getMethodName(); void setMethodName(String methodName); String getFileName(); int getLineNumber(); void setLocation(String fileName, int lineNumber); @Override int hashCode(); @Override boolean equals(Object o); @Override String toString(); boolean isNative(); boolean isUnknown(); static final int IS_NATIVE; static final int IS_UNKNOWN; }### Answer:
@Test public void testToString() { String className = "clazz"; String method = "method"; String fileName = "file.java"; int lineNumber = 42; Frame frame = new Frame(className, method, fileName, lineNumber); assertThat(frame.toString(), not(emptyString())); }