Exploration of new features in PHP 7: How to use expectations syntax to simplify assertion writing

Exploration of new features in PHP 7: How to use the expectations syntax to simplify assertion writing

Introduction:
With the release of PHP 7, developers have welcomed many exciting new features and improvements. One of the most interesting features is the expectations syntax. This new syntax can greatly simplify writing assertions, making it easier to write code that is highly readable and easy to maintain. This article will introduce the basic usage of expectations syntax and demonstrate its advantages through some specific code examples.

What is expectations syntax?
In PHP, assertions are a method used to verify conditions in code. The original assertion syntax uses the assert() function, which takes a conditional expression as a parameter and raises an assertion error when the condition is false. However, writing assertions this way is verbose and unintuitive.

The expectations syntax simplifies the writing of assertions through the new assertion function expect(). We can use the expect() function to assert whether a value or expression meets expectations. When the assertion fails, the expect() function will throw a custom assertion exception, which contains the error message and the location of the assertion failure.

Usage of expectations syntax:
Let us use some code examples to show how to use expectations syntax to improve the writing of assertions.

Example 1: Simple assertion
Suppose we have a function add() that adds two numbers and returns the result. We can use the expectations syntax to verify that the return value of a function is as expected.

function add($a, $b) {
    return $a + $b;
}

// 使用expectations语法断言add()函数的返回值是否为3
expect(add(1, 2))->toBe(3);

In this example, we use the expect() function to assert whether the return value of add(1, 2) is equal to 3. If the assertion fails, the expect() function will throw an AssertionException, which contains the details of the assertion failure.

Example 2: Assert Array
We can also use the expectations syntax to assert whether the array meets expectations. The following example shows how to use toBe() and toContain() to verify the value of an array.

$data = ['apple', 'banana', 'orange'];

// 断言数组$data的长度等于3
expect($data)->toHaveLength(3);

// 断言数组$data中包含'banana'这个值
expect($data)->toContain('banana');

In this example, we use the toHaveLength() and toContain() functions to assert the length of the array and whether the array contains a specific value.

Example 3: Custom assertion function
In addition to the existing assertion functions, we can also customize some assertion functions. Doing so allows us to write more expressive assertions based on the needs of the project.

function isEven($num) {
    return $num % 2 == 0;
}

// 断言数字6是一个偶数
expect(6)->toBeTrue(isEven);

In this example, we define a custom assertion function isEven(), which is used to determine whether a number is even. Then, we use the toBeTrue() function to assert whether the number 6 is an even number.

Conclusion:
PHP 7’s expectations syntax provides us with a simpler and more intuitive way to write assertions. By using the expect() function, we can more easily write code that is highly readable and easy to maintain. I hope the sample code provided in this article can help you better understand and use the expectations syntax. Now, it's time to try this powerful new feature in your projects!

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