[10.x] Adds testing helpers for Precognition

src/Illuminate/Foundation/Testing/Concerns/MakesHttpRequests.php

@@ -309,6 +309,16 @@ public function from(string $url)
         return $this->withHeader('referer', $url);
     }
 
+    /**
+     * Set the precognition header
+     *
+     * @return $this
+     */
+    public function usingPrecognition()
+    {
+        return $this->withHeader('Precognition', 'true');
+    }
+
     /**
      * Visit the given URI with a GET request.
      *

src/Illuminate/Testing/TestResponse.php

@@ -1417,6 +1417,25 @@ public function assertSessionMissing($key)
         return $this;
     }
 
+    /**
+     * Assert that the Precognition request was successful
+     *
+     * @return $this
+     */
+    public function assertPrecognitionSuccess()
+    {
+        PHPUnit::assertTrue(
+            $this->headers->has('Precognition-Success'), 'Precognition-Success Header not present on response.'
+        );
+
+        PHPUnit::assertSame(
+            'True', $this->headers->get('Precognition-Success'),
+            'Precognition-Success Header was found, but the value is not `True`.'
+        );
+
+        return $this;
+    }
+
     /**
      * Get the current session store.
      *

tests/Foundation/Testing/Concerns/MakesHttpRequestsTest.php

@@ -186,6 +186,13 @@ public function testFollowingRedirectsTerminatesInExpectedOrder()
 
         $this->assertEquals(['from', 'to'], $callOrder);
     }
+
+    public function testUsingPrecognition()
+    {
+        $this->usingPrecognition();
+
+        $this->assertSame('true', $this->defaultHeaders['Precognition']);
+    }
 }
 
 class MyMiddleware

tests/Testing/TestResponseTest.php

@@ -1035,6 +1035,32 @@ public function testAssertHeaderMissing()
         $response->assertHeaderMissing('Location');
     }
 
+    public function testAssertPrecognitionSuccessfulWithMissingHeader()
+    {
+        $this->expectException(AssertionFailedError::class);
+        $this->expectExceptionMessage('Precognition-Success Header not present on response.');
+
+        $baseResponse = new Response();
+
+        $response = TestResponse::fromBaseResponse($baseResponse);
+
+        $response->assertPrecognitionSuccess();
+    }
+
+    public function testAssertPrecognitionSuccessfulWithIncorrectValue()
+    {
+        $this->expectException(AssertionFailedError::class);
+        $this->expectExceptionMessage('Precognition-Success Header was found, but the value is not `True`.');
+
+        $baseResponse = tap(new Response, function ($response) {
+            $response->header('Precognition-Success', '');
+        });
+
+        $response = TestResponse::fromBaseResponse($baseResponse);
+
+        $response->assertPrecognitionSuccess();
+    }
+
     public function testAssertJsonWithArray()
     {
         $response = TestResponse::fromBaseResponse(new Response(new JsonSerializableSingleResourceStub));