[feature] Assert that an header is not present (#98)

Author: nitneuk

README.md

@@ -227,6 +227,7 @@ $browser
     ->assertRedirected() // 3xx status code
     ->assertHeaderEquals('Content-Type', 'text/html; charset=UTF-8')
     ->assertHeaderContains('Content-Type', 'html')
+    ->assertHeaderEquals('X-Not-Present-Header', null)
 
     // helpers for quickly checking the content type
     ->assertJson()

src/Browser/KernelBrowser.php

@@ -414,7 +414,7 @@ final public function assertRedirected(): self
     /**
      * @return static
      */
-    final public function assertHeaderEquals(string $header, string $expected): self
+    final public function assertHeaderEquals(string $header, ?string $expected): self
     {
         $this->session()->assert()->responseHeaderEquals($header, $expected);
 

tests/KernelBrowserTests.php

@@ -233,6 +233,7 @@ public function response_header_assertions(): void
             ->visit('/page1')
             ->assertHeaderEquals('Content-Type', 'text/html; charset=UTF-8')
             ->assertHeaderContains('Content-Type', 'text/html')
+            ->assertHeaderEquals('X-Not-Present-Header', null)
         ;
     }