# Adding Asserts Our basic Hurl file is now: ```hurl # Our first Hurl file, just checking # that our server is up and running. GET http://localhost:3000 HTTP 200 ``` Currently, we're just checking that our home page is responding with a `200 OK` HTTP status code. But we also want to check the _content_ of our home page, to ensure that everything is ok. To check the response of an HTTP request with Hurl, we have to _describe_ tests that the response content must pass. To do so, we're going to use [asserts]. As our endpoint is serving HTML content, it makes sense to use [XPath asserts]. If we want to test a REST API or any sort of API that serves JSON content, we could use [JSONPath asserts] instead. There are other type of asserts but every one shares the same structure. So, let's look how to write a [XPath asserts]. ## HTML Body Test ### Structure of an assert
xpath "string(//h1)"query containspredicate type "Hello"predicate value
An assert consists of a query and a predicate. As we want to test the value of the HTML title tag, we're going to use the [XPath expression] `string(//head/title)`. 1. Asserts are written in an `[Asserts]` section, so modify `basic.hurl` file: ```hurl # Our first Hurl file, just checking # that our server is up and running. GET http://localhost:3000 HTTP 200 [Asserts] xpath "string(//head/title)" == "Movies Box" ``` 2. Run `basic.hurl`: ```shell $ hurl --test basic.hurl basic.hurl: Running [1/1] basic.hurl: Success (1 request(s) in 19 ms) -------------------------------------------------------------------------------- Executed files: 1 Succeeded files: 1 (100.0%) Failed files: 0 (0.0%) Duration: 19 ms ``` There is no error so everything is good! 3. Modify the test value to "Movies Bax" ```hurl # Our first Hurl file, just checking # that our server is up and running. GET http://localhost:3000 HTTP 200 [Asserts] xpath "string(//head/title)" == "Movies Bax" ``` 4. Run `basic.hurl`: ```shell $ hurl --test basic.hurl basic.hurl: Running [1/1] error: Assert failure --> basic.hurl:7:0 |  7 | xpath "string(//head/title)" == "Movies Bax" | actual: string  | expected: string  | basic.hurl: Failure (1 request(s) in 22 ms) -------------------------------------------------------------------------------- Executed files: 1 Succeeded files: 0 (0.0%) Failed files: 1 (100.0%) Duration: 23 ms ``` Hurl has failed now and provides information on which assert is not valid. ### Typed predicate Decompose our assert: - __`xpath "string(//head/title)"`__ is the XPath query - __`== "Movies Box"`__ is our predicate to test the query against You can note that tested values are typed: - `xpath "string(//head/title)" ==` __`"true"`__ tests that the XPath expression is returning a string, and this string is equal to the string `true` - `xpath "boolean(//head/title)" ==` __`true`__ tests that the XPath expression is returning a boolean, and the boolean is `true` Some queries can also return collections. For instance, the XPath expression `//button` is returning all the button elements present in the [DOM]. We can use it to ensure that we have exactly two `

` tag on our home page, with [`count`]: 1. Add a new assert in `basic.hurl` to check the number of `

` tags: ```hurl # Checking our home page: GET http://localhost:3000 HTTP 200 [Asserts] xpath "string(//head/title)" == "Movies Box" xpath "//h3" count == 2 ``` 2. We can also check each `

`'s content: ```hurl # Checking our home page: GET http://localhost:3000 HTTP 200 [Asserts] xpath "string(//head/title)" == "Movies Box" xpath "//h3" count == 2 xpath "string((//h3)[1])" contains "Popular" xpath "string((//h3)[2])" contains "Featured Today" ``` > XPath queries can sometimes be a little tricky to write but modern browsers can help writing these expressions. > Try open the Javascript console of your browser (Firefox, Safari or Chrome) and type `$x("string(//head/title)")` > then press Return. You should see the result of your XPath query. 3. Run `basic.hurl` and check that every assert has been successful: ```shell $ hurl --test basic.hurl basic.hurl: Running [1/1] basic.hurl: Success (1 request(s) in 11 ms) -------------------------------------------------------------------------------- Executed files: 1 Succeeded files: 1 (100.0%) Failed files: 0 (0.0%) Duration: 15 ms ``` ## HTTP Headers Test We are also going to add tests on the HTTP response headers with explicit [`header` asserts]. As our endpoint is serving UTF-8 encoded HTML content, we can check the value of the [`Content-Type` response header]. 1. Add a new assert at the end of `basic.hurl` to test the value of the `Content-Type` HTTP header: ```hurl # Checking our home page: GET http://localhost:3000 HTTP 200 [Asserts] xpath "string(//head/title)" == "Movies Box" xpath "//h3" count == 2 xpath "string((//h3)[1])" contains "Popular" xpath "string((//h3)[2])" contains "Featured Today" # Testing HTTP response headers: header "Content-Type" == "text/html; charset=utf-8" ``` > Our HTTP response has only one `Content-Type` header, so we're testing this header value as string. > The same header could be present multiple times in an HTTP response, with different values. > In this case, the `header` query will return collections and could be tested with > [`count`] or [`includes`]. For HTTP headers, we can also use an [implicit header assert]. You can use either implicit or explicit header assert: the implicit one allows you to only check the exact value of the header, while the explicit one allows you to use other [predicates] (like `contains`, `startsWith`, `matches` etc...). 2. Replace the explicit assert with [implicit header assert]: ```hurl # Checking our home page: GET http://localhost:3000 HTTP 200 # Implicitly testing response headers: Content-Type: text/html; charset=utf-8 [Asserts] xpath "string(//head/title)" == "Movies Box" xpath "//h3" count == 2 xpath "string((//h3)[1])" contains "Popular" xpath "string((//h3)[2])" contains "Featured Today" ``` The line `Content-Type: text/html; charset=utf-8` is testing that the header `Content-Type` is present in the response, and its value must be exactly `text/html; charset=utf-8`. > In the implicit assert, quotes in the header value are part of the value itself. Finally, we want to check that our server is creating a new session. When creating a new session, our Express application returns a [`Set-Cookie` HTTP response header]. So to test it, we can modify our Hurl file with another header assert. 3. Add a header assert on `Set-Cookie` header: ```hurl # Checking our home page: GET http://localhost:3000 HTTP 200 [Asserts] xpath "string(//head/title)" == "Movies Box" xpath "//h3" count == 2 xpath "string((//h3)[1])" contains "Popular" xpath "string((//h3)[2])" contains "Featured Today" # Testing HTTP response headers: header "Content-Type" == "text/html; charset=utf-8" header "Set-Cookie" startsWith "x-session-id=" ``` For `Set-Cookie` header, we can use the specialized [Cookie assert]. Not only we'll be able to easily tests [cookie attributes] (like `HttpOnly`, or `SameSite`), but also it simplifies tests on cookies, particularly when there are multiple `Set-Cookie` header in the HTTP response. > Hurl is not a browser, one can see it as syntactic sugar over [curl]. Hurl > has no JavaScript runtime and stays close to the HTTP layer. With others tools relying on headless browser, it can be > difficult to access some HTTP requests attributes, like `Set-Cookie` header. So to test that our server is responding with a `HttpOnly` session cookie, we can modify our file and add cookie asserts. 4. Add two cookie asserts on the cookie `x-session-id`: ```hurl # Checking our home page: GET http://localhost:3000 HTTP 200 [Asserts] xpath "string(//head/title)" == "Movies Box" xpath "//h3" count == 2 xpath "string((//h3)[1])" contains "Popular" xpath "string((//h3)[2])" contains "Featured Today" # Testing HTTP response headers: header "Content-Type" == "text/html; charset=utf-8" cookie "x-session-id" exists cookie "x-session-id[HttpOnly]" exists ``` 5. Run `basic.hurl` and check that every assert has been successful: ```shell $ hurl --test basic.hurl basic.hurl: Running [1/1] basic.hurl: Success (1 request(s) in 11 ms) -------------------------------------------------------------------------------- Executed files: 1 Succeeded files: 1 (100.0%) Failed files: 0 (0.0%) Duration: 20 ms ``` ## Performance Test > TODO: add duration assert ## Recap Our Hurl file is now around 10 lines long, but we're already testing a lot on our home page: - we are testing that our home page is responding with a `200 OK` - we are checking the basic structure of our page: a title, 2 `

` tags - we are checking that the content type is UTF-8 HTML - we are checking that our server has created a session, and that the cookie session has the `HttpOnly` attribute You can see now that launching and running requests with Hurl is fast, _really_ fast. In the next session, we're going to see how we chain request tests, and how we add basic check on a REST API. [asserts]: /docs/asserting-response.md [XPath asserts]: /docs/asserting-response.md#xpath-assert [JSONPath asserts]: /docs/asserting-response.md#jsonpath-assert [XPath expression]: https://en.wikipedia.org/wiki/XPath [DOM]: https://en.wikipedia.org/wiki/Document_Object_Model [`header` asserts]: /docs/asserting-response.md#header-assert [`Content-Type` response header]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Type [implicit header assert]: /docs/asserting-response.md#headers [predicates]: /docs/asserting-response.md#predicates [`Set-Cookie` HTTP response header]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Cookies#creating_cookies [Cookie assert]: /docs/asserting-response.md#cookie-assert [cookie attributes]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie#attributes [curl]: https://curl.se [`count`]: /docs/filters.md#count [`includes`]: /docs/asserting-response.md#predicates