diff --git a/composer.json b/composer.json
index e708b1e..a6022c2 100644
--- a/composer.json
+++ b/composer.json
@@ -19,6 +19,7 @@
         "symfony/css-selector": "^4.4|^5.0",
         "symfony/framework-bundle": "^4.4|^5.0",
         "symfony/polyfill-php80": "^1.20",
+        "zenstruck/assert": "^1.0",
         "zenstruck/callback": "^1.1"
     },
     "require-dev": {
diff --git a/src/Browser.php b/src/Browser.php
index c5aebe6..ac96bdc 100644
--- a/src/Browser.php
+++ b/src/Browser.php
@@ -9,12 +9,12 @@
 use Behat\Mink\Mink;
 use Behat\Mink\Session;
 use Behat\Mink\WebAssert;
-use PHPUnit\Framework\Assert as PHPUnit;
 use Symfony\Component\DomCrawler\Crawler;
 use Symfony\Component\Filesystem\Filesystem;
+use Zenstruck\Browser\Assertion\MinkAssertion;
+use Zenstruck\Browser\Assertion\SameUrlAssertion;
 use Zenstruck\Browser\Component;
 use Zenstruck\Browser\Response;
-use Zenstruck\Browser\Test\Constraint\UrlMatches;
 use Zenstruck\Callback\Parameter;
 
 /**
@@ -57,13 +57,13 @@ final public function visit(string $uri): self
     }
 
     /**
-     * @param array $parts The url parts to check (@see parse_url)
+     * @param array $parts The url parts to check {@see parse_url} (use empty array for "all")
      *
      * @return static
      */
     final public function assertOn(string $expected, array $parts = ['path', 'query', 'fragment']): self
     {
-        PHPUnit::assertThat($expected, new UrlMatches($this->minkSession()->getCurrentUrl(), $parts));
+        Assert::run(new SameUrlAssertion($this->minkSession()->getCurrentUrl(), $expected, $parts));
 
         return $this;
     }
@@ -75,10 +75,7 @@ final public function assertOn(string $expected, array $parts = ['path', 'query'
      */
     final public function assertNotOn(string $expected, array $parts = ['path', 'query', 'fragment']): self
     {
-        PHPUnit::assertThat(
-            $expected,
-            PHPUnit::logicalNot(new UrlMatches($this->minkSession()->getCurrentUrl(), $parts))
-        );
+        Assert::not(new SameUrlAssertion($this->minkSession()->getCurrentUrl(), $expected, $parts));
 
         return $this;
     }
@@ -374,12 +371,11 @@ final public function assertSelected(string $selector, string $expected): self
     {
         try {
             $field = $this->webAssert()->fieldExists($selector);
-            PHPUnit::assertTrue(true);
         } catch (ExpectationException $e) {
-            PHPUnit::fail($e->getMessage());
+            Assert::fail($e->getMessage());
         }
 
-        PHPUnit::assertContains($expected, (array) $field->getValue());
+        Assert::that((array) $field->getValue())->contains($expected);
 
         return $this;
     }
@@ -391,12 +387,11 @@ final public function assertNotSelected(string $selector, string $expected): sel
     {
         try {
             $field = $this->webAssert()->fieldExists($selector);
-            PHPUnit::assertTrue(true);
         } catch (ExpectationException $e) {
-            PHPUnit::fail($e->getMessage());
+            Assert::fail($e->getMessage());
         }
 
-        PHPUnit::assertNotContains($expected, (array) $field->getValue());
+        Assert::that((array) $field->getValue())->doesNotContain($expected);
 
         return $this;
     }
@@ -493,12 +488,7 @@ final protected function documentElement(): DocumentElement
      */
     final protected function wrapMinkExpectation(callable $callback): self
     {
-        try {
-            $callback();
-            PHPUnit::assertTrue(true);
-        } catch (ExpectationException $e) {
-            PHPUnit::fail($e->getMessage());
-        }
+        Assert::run(new MinkAssertion($callback));
 
         return $this;
     }
diff --git a/src/Browser/Assertion/MinkAssertion.php b/src/Browser/Assertion/MinkAssertion.php
new file mode 100644
index 0000000..0f407d8
--- /dev/null
+++ b/src/Browser/Assertion/MinkAssertion.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Zenstruck\Browser\Assertion;
+
+use Behat\Mink\Exception\ExpectationException;
+use Zenstruck\Assert\AssertionFailed;
+
+/**
+ * @author Kevin Bond <kevinbond@gmail.com>
+ *
+ * @internal
+ */
+final class MinkAssertion
+{
+    /** @var callable */
+    private $callback;
+
+    public function __construct(callable $callback)
+    {
+        $this->callback = $callback;
+    }
+
+    public function __invoke(): void
+    {
+        try {
+            ($this->callback)();
+        } catch (ExpectationException $e) {
+            AssertionFailed::throw($e->getMessage());
+        }
+    }
+}
diff --git a/src/Browser/Assertion/SameUrlAssertion.php b/src/Browser/Assertion/SameUrlAssertion.php
new file mode 100644
index 0000000..77a35f8
--- /dev/null
+++ b/src/Browser/Assertion/SameUrlAssertion.php
@@ -0,0 +1,77 @@
+<?php
+
+namespace Zenstruck\Browser\Assertion;
+
+use Zenstruck\Assert\Assertion\Negatable;
+use Zenstruck\Assert\AssertionFailed;
+
+/**
+ * @author Kevin Bond <kevinbond@gmail.com>
+ *
+ * @internal
+ */
+final class SameUrlAssertion implements Negatable
+{
+    private string $current;
+    private string $expected;
+    private array $partsToMatch;
+
+    public function __construct(string $current, string $expected, array $partsToMatch = [])
+    {
+        $this->current = $current;
+        $this->expected = $expected;
+        $this->partsToMatch = $partsToMatch;
+    }
+
+    public function __invoke(): void
+    {
+        $parsedCurrent = $this->parseUrl($this->current);
+        $parsedExpected = $this->parseUrl($this->expected);
+
+        if ($parsedCurrent === $parsedExpected) {
+            return;
+        }
+
+        AssertionFailed::throw(
+            'Expected current URL ({current}) to be "{expected}" (comparing parts: "{parts}").',
+            \array_merge($this->context(), [
+                'compare_actual' => $parsedCurrent,
+                'compare_expected' => $parsedExpected,
+            ])
+        );
+    }
+
+    public function notFailure(): AssertionFailed
+    {
+        return new AssertionFailed(
+            'Expected current URL ({current}) to not be "{expected}" (comparing parts: "{parts}").',
+            $this->context()
+        );
+    }
+
+    private function context(): array
+    {
+        return [
+            'current' => $this->current,
+            'expected' => $this->expected,
+            'parts' => \implode(', ', $this->partsToMatch),
+        ];
+    }
+
+    private function parseUrl(string $url): array
+    {
+        $parts = \parse_url(\urldecode($url));
+
+        if (empty($this->partsToMatch)) {
+            return $parts;
+        }
+
+        foreach (\array_keys($parts) as $part) {
+            if (!\in_array($part, $this->partsToMatch, true)) {
+                unset($parts[$part]);
+            }
+        }
+
+        return $parts;
+    }
+}
diff --git a/src/Browser/BrowserKitBrowser.php b/src/Browser/BrowserKitBrowser.php
index cf9aced..2921ae1 100644
--- a/src/Browser/BrowserKitBrowser.php
+++ b/src/Browser/BrowserKitBrowser.php
@@ -2,9 +2,9 @@
 
 namespace Zenstruck\Browser;
 
-use PHPUnit\Framework\Assert as PHPUnit;
 use Symfony\Component\BrowserKit\AbstractBrowser;
 use Symfony\Component\HttpKernel\Profiler\Profile;
+use Zenstruck\Assert;
 use Zenstruck\Browser;
 use Zenstruck\Browser\Mink\BrowserKitDriver;
 
@@ -171,7 +171,9 @@ final public function assertStatus(int $expected): self
      */
     final public function assertSuccessful(): self
     {
-        PHPUnit::assertTrue($this->response()->isSuccessful(), "Expected successful status code (2xx), [{$this->response()->statusCode()}] received.");
+        Assert::true($this->response()->isSuccessful(), 'Expected successful status code (2xx) but got {actual}.', [
+            'actual' => $this->response()->statusCode(),
+        ]);
 
         return $this;
     }
@@ -185,7 +187,9 @@ final public function assertRedirected(): self
             throw new \RuntimeException('Cannot assert redirected if not intercepting redirects. Call ->interceptRedirects() before making the request.');
         }
 
-        PHPUnit::assertTrue($this->response()->isRedirect(), "Expected redirect status code (3xx), [{$this->response()->statusCode()}] received.");
+        Assert::true($this->response()->isRedirect(), 'Expected redirect status code (3xx) but got {actual}.', [
+            'actual' => $this->response()->statusCode(),
+        ]);
 
         return $this;
     }
@@ -226,7 +230,7 @@ final public function assertJson(string $expectedContentType = 'json'): self
      */
     final public function assertJsonMatches(string $expression, $expected): self
     {
-        PHPUnit::assertSame($expected, $this->response()->assertJson()->search($expression));
+        Assert::that($this->response()->assertJson()->search($expression))->is($expected);
 
         return $this;
     }
diff --git a/src/Browser/PantherBrowser.php b/src/Browser/PantherBrowser.php
index dbdf769..47be657 100644
--- a/src/Browser/PantherBrowser.php
+++ b/src/Browser/PantherBrowser.php
@@ -2,10 +2,10 @@
 
 namespace Zenstruck\Browser;
 
-use PHPUnit\Framework\Assert as PHPUnit;
 use Symfony\Component\Filesystem\Filesystem;
 use Symfony\Component\Panther\Client;
 use Symfony\Component\VarDumper\VarDumper;
+use Zenstruck\Assert;
 use Zenstruck\Browser;
 use Zenstruck\Browser\Mink\PantherDriver;
 use Zenstruck\Browser\Response\PantherResponse;
@@ -53,11 +53,11 @@ final public function setConsoleLogDir(string $dir): self
     final public function follow(string $link): self
     {
         if (!$element = $this->documentElement()->findLink($link)) {
-            PHPUnit::fail(\sprintf('Link "%s" not found.', $link));
+            Assert::fail('Link "%s" not found.', [$link]);
         }
 
         if (!$element->isVisible()) {
-            PHPUnit::fail(\sprintf('Link "%s" is not visible.', $link));
+            Assert::fail('Link "%s" is not visible.', [$link]);
         }
 
         $this->documentElement()->clickLink($link);
@@ -73,7 +73,7 @@ final public function assertVisible(string $selector): self
         return $this->wrapMinkExpectation(function() use ($selector) {
             $element = $this->webAssert()->elementExists('css', $selector);
 
-            PHPUnit::assertTrue($element->isVisible());
+            Assert::true($element->isVisible(), 'Expected element "%s" to be visible but it isn\'t.', [$selector]);
         });
     }
 
@@ -85,12 +85,12 @@ final public function assertNotVisible(string $selector): self
         $element = $this->documentElement()->find('css', $selector);
 
         if (!$element) {
-            PHPUnit::assertTrue(true);
+            Assert::pass();
 
             return $this;
         }
 
-        PHPUnit::assertFalse($element->isVisible());
+        Assert::false($element->isVisible(), 'Expected element "%s" to not be visible but it is.', [$selector]);
 
         return $this;
     }
diff --git a/src/Browser/Response.php b/src/Browser/Response.php
index 9014f54..de048d0 100644
--- a/src/Browser/Response.php
+++ b/src/Browser/Response.php
@@ -3,8 +3,8 @@
 namespace Zenstruck\Browser;
 
 use Behat\Mink\Session;
-use PHPUnit\Framework\Assert as PHPUnit;
 use Symfony\Component\VarDumper\VarDumper;
+use Zenstruck\Assert;
 use Zenstruck\Browser\Response\DomResponse;
 use Zenstruck\Browser\Response\HtmlResponse;
 use Zenstruck\Browser\Response\JsonResponse;
@@ -60,7 +60,7 @@ final public function body(): string
     final public function assertJson(): JsonResponse
     {
         if (!$this instanceof JsonResponse) {
-            PHPUnit::fail('Not a json response.');
+            Assert::fail('Not a json response.');
         }
 
         return $this;
@@ -69,7 +69,7 @@ final public function assertJson(): JsonResponse
     final public function assertXml(): XmlResponse
     {
         if (!$this instanceof XmlResponse) {
-            PHPUnit::fail('Not an xml response.');
+            Assert::fail('Not an xml response.');
         }
 
         return $this;
@@ -78,7 +78,7 @@ final public function assertXml(): XmlResponse
     final public function assertHtml(): HtmlResponse
     {
         if (!$this instanceof HtmlResponse) {
-            PHPUnit::fail('Not an html response.');
+            Assert::fail('Not an html response.');
         }
 
         return $this;
@@ -87,7 +87,7 @@ final public function assertHtml(): HtmlResponse
     final public function assertDom(): DomResponse
     {
         if (!$this instanceof DomResponse) {
-            PHPUnit::fail('Not an DOM response.');
+            Assert::fail('Not an DOM response.');
         }
 
         return $this;
diff --git a/src/Browser/Test/Constraint/UrlMatches.php b/src/Browser/Test/Constraint/UrlMatches.php
deleted file mode 100644
index c3c0e38..0000000
--- a/src/Browser/Test/Constraint/UrlMatches.php
+++ /dev/null
@@ -1,54 +0,0 @@
-<?php
-
-namespace Zenstruck\Browser\Test\Constraint;
-
-use PHPUnit\Framework\Constraint\Constraint;
-
-/**
- * @author Kevin Bond <kevinbond@gmail.com>
- *
- * @internal
- */
-final class UrlMatches extends Constraint
-{
-    private array $partsToMatch;
-    private array $url;
-
-    public function __construct(string $url, array $partsToMatch = [])
-    {
-        $this->partsToMatch = $partsToMatch;
-        $this->url = $this->parseUrl($url);
-    }
-
-    public function toString(): string
-    {
-        return 'matches '.$this->exporter()->export($this->url);
-    }
-
-    protected function matches($other): bool
-    {
-        return $this->parseUrl($other) === $this->url;
-    }
-
-    protected function failureDescription($other): string
-    {
-        return parent::failureDescription($this->parseUrl($other));
-    }
-
-    private function parseUrl(string $url): array
-    {
-        $parts = \parse_url(\urldecode($url));
-
-        if (empty($this->partsToMatch)) {
-            return $parts;
-        }
-
-        foreach (\array_keys($parts) as $part) {
-            if (!\in_array($part, $this->partsToMatch, true)) {
-                unset($parts[$part]);
-            }
-        }
-
-        return $parts;
-    }
-}