function isConfigurable(obj, name) {
    try {
        delete obj[name];
    } catch (e) {
        if (!(e instanceof TypeError)) {
            $ERROR("Expected TypeError, got " + e);
        }
    }
    return !Object.prototype.hasOwnProperty.call(obj, name);
}

function isEnumerable(obj, name) {
    return Object.prototype.hasOwnProperty.call(obj, name) &&
        Object.prototype.propertyIsEnumerable.call(obj, name);
}

function isEqualTo(obj, name, expectedValue) {
    var actualValue = obj[name];

    return assert._isSameValue(actualValue, expectedValue);
}

function isWritable(obj, name, verifyProp, value) {
    var newValue = value || "unlikelyValue";
    var hadValue = Object.prototype.hasOwnProperty.call(obj, name);
    var oldValue = obj[name];
    var writeSucceeded;

    try {
        obj[name] = newValue;
    } catch (e) {
        if (!(e instanceof TypeError)) {
            $ERROR("Expected TypeError, got " + e);
        }
    }

    writeSucceeded = isEqualTo(obj, verifyProp || name, newValue);

    // Revert the change only if it was successful (in other cases, reverting
    // is unnecessary and may trigger exceptions for certain property
    // configurations)
    if (writeSucceeded) {
      if (hadValue) {
        obj[name] = oldValue;
      } else {
        delete obj[name];
      }
    }

    return writeSucceeded;
}

function verifyEqualTo(obj, name, value) {
    if (!isEqualTo(obj, name, value)) {
        $ERROR("Expected obj[" + String(name) + "] to equal " + value +
                   ", actually " + obj[name]);
    }
}

function verifyWritable(obj, name, verifyProp, value) {
    if (!verifyProp) {
        assert(Object.getOwnPropertyDescriptor(obj, name).writable,
               "Expected obj[" + String(name) + "] to have writable:true.");
    }
    if (!isWritable(obj, name, verifyProp, value)) {
        $ERROR("Expected obj[" + String(name) + "] to be writable, but was not.");
    }
}

function verifyNotWritable(obj, name, verifyProp, value) {
    if (!verifyProp) {
        assert(!Object.getOwnPropertyDescriptor(obj, name).writable,
               "Expected obj[" + String(name) + "] to have writable:false.");
    }
    if (isWritable(obj, name, verifyProp)) {
        $ERROR("Expected obj[" + String(name) + "] NOT to be writable, but was.");
    }
}

function verifyEnumerable(obj, name) {
    assert(Object.getOwnPropertyDescriptor(obj, name).enumerable,
           "Expected obj[" + String(name) + "] to have enumerable:true.");
    if (!isEnumerable(obj, name)) {
        $ERROR("Expected obj[" + String(name) + "] to be enumerable, but was not.");
    }
}

function verifyNotEnumerable(obj, name) {
    assert(!Object.getOwnPropertyDescriptor(obj, name).enumerable,
           "Expected obj[" + String(name) + "] to have enumerable:false.");
    if (isEnumerable(obj, name)) {
        $ERROR("Expected obj[" + String(name) + "] NOT to be enumerable, but was.");
    }
}

function verifyConfigurable(obj, name) {
    assert(Object.getOwnPropertyDescriptor(obj, name).configurable,
           "Expected obj[" + String(name) + "] to have configurable:true.");
    if (!isConfigurable(obj, name)) {
        $ERROR("Expected obj[" + String(name) + "] to be configurable, but was not.");
    }
}

function verifyNotConfigurable(obj, name) {
    assert(!Object.getOwnPropertyDescriptor(obj, name).configurable,
           "Expected obj[" + String(name) + "] to have configurable:false.");
    if (isConfigurable(obj, name)) {
        $ERROR("Expected obj[" + String(name) + "] NOT to be configurable, but was.");
    }
}