c.Mat3.toEulerZXZ(m0, euler);

    assertRoughlyEquals(roll, euler[0], goog.vec.EPSILON);
    assertRoughlyEquals(tilt, euler[1], goog.vec.EPSILON);
    assertRoughlyEquals(yaw, euler[2], goog.vec.EPSILON);

    // Test negative tilt now.
    goog.vec.Mat3.makeRotate(m0, roll, 0, 0, 1);
    goog.vec.Mat3.rotate(m0, -tilt, 1, 0, 0);
    goog.vec.Mat3.rotate(m0, yaw, 0, 0, 1);

    goog.vec.Mat3.makeEulerZXZ(m1, roll, -tilt, yaw);
    assertElementsRoughlyEqual(m0, m1, goog.vec.EPSILON);

    var euler = [0, 