Jasmine and Angular: Including Expressions with TypeScript

If you're building an Angular application with TypeScript, you'll likely need to use expressions in your code. In this tutorial, we'll cover how to include expressions using Jasmine and Angular.

Setting Up Jasmine

Before we can start including expressions, we need to set up Jasmine in our Angular project. To do this, we need to install the Jasmine NPM package and add the following scripts to our package.json file:

"scripts": {
    "test": "ng test --no-watch --code-coverage",
    "test:dev": "ng test"
},

The first script is for running tests with code coverage, and the second is for running tests in watch mode. Now we can install Jasmine:

npm install jasmine --save-dev

Writing Tests with Jasmine

To use expressions, we need to write tests that expect certain values to be returned. For example, let's say we have a simple function that multiplies two numbers together:

function multiply(num1: number, num2: number): number {
  return num1 * num2;
}

We can write a test for this function using Jasmine like this:

describe('multiply', () => {
  it('should correctly multiply two numbers', () => {
    const result = multiply(2, 3);
    expect(result).toEqual(6);
  });
});

In this test, we call the multiply function with the arguments 2 and 3, and then use the expect function to check that the result is equal to 6.

Including Expressions

To include expressions in your tests, you can use the {{ }} syntax in your test description:

describe('multiply', () => {
  it('should correctly multiply {{ num1 }} and {{ num2 }}', () => {
    const result = multiply({{ num1 }}, {{ num2 }});
    expect(result).toEqual({{ expectedResult }});
  });
});

In this example, we've used expressions to specify the values of num1, num2, and expectedResult. To make this work, we need to pass these values to the it function as parameters:

describe('multiply', () => {
  it('should correctly multiply {{ num1 }} and {{ num2 }}', () => {
    const result = multiply(num1, num2);
    expect(result).toEqual(expectedResult);
  }, {
    params: {
      num1: 2,
      num2: 3,
      expectedResult: 6
    }
  });
});

In this example, we've specified the values of num1, num2, and expectedResult as parameters to the it function. The params object allows us to specify these values when we run our tests.

Conclusion

In this tutorial, we've covered how to include expressions in your Jasmine tests when building an Angular application with TypeScript. With these techniques, you can write more expressive and flexible tests that allow you to test a wider range of scenarios.