diff --git a/CHANGELOG.md b/CHANGELOG.md
index ffff6884..1557685b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@ For a full diff see [`7afa59c...main`][7afa59c...main].
 * Added `Comparator\DurationComparator` ([#18]), by [@localheinz]
 * Added `SlowTestReporter` ([#19]), by [@localheinz]
 * Extracted `TimeKeeper` ([#22]), by [@localheinz]
+* Extracted `Collector` ([#23]), by [@localheinz]
 
 ### Changed
 
@@ -36,5 +37,6 @@ For a full diff see [`7afa59c...main`][7afa59c...main].
 [#20]: https://github.com/ergebnis/phpunit-slow-test-detector/pull/20
 [#21]: https://github.com/ergebnis/phpunit-slow-test-detector/pull/21
 [#22]: https://github.com/ergebnis/phpunit-slow-test-detector/pull/22
+[#23]: https://github.com/ergebnis/phpunit-slow-test-detector/pull/23
 
 [@localheinz]: https://github.com/localheinz
diff --git a/src/Collector.php b/src/Collector.php
new file mode 100644
index 00000000..69f16bf0
--- /dev/null
+++ b/src/Collector.php
@@ -0,0 +1,63 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright (c) 2021 Andreas Möller
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE.md file that was distributed with this source code.
+ *
+ * @see https://github.com/ergebnis/phpunit-slow-test-detector
+ */
+
+namespace Ergebnis\PHPUnit\SlowTestDetector;
+
+use PHPUnit\Event;
+
+final class Collector
+{
+    /**
+     * @var array<string, SlowTest>
+     */
+    private array $slowTests = [];
+
+    public function collect(SlowTest $slowTest): void
+    {
+        $key = self::key($slowTest->test());
+
+        if (\array_key_exists($key, $this->slowTests)) {
+            $previousSlowTest = $this->slowTests[$key];
+
+            if (!$slowTest->duration()->isGreaterThan($previousSlowTest->duration())) {
+                return;
+            }
+
+            $this->slowTests[$key] = $slowTest;
+
+            return;
+        }
+
+        $this->slowTests[$key] = $slowTest;
+    }
+
+    /**
+     * @phpstan-return list<SlowTest>
+     * @psalm-return list<SlowTest>
+     *
+     * @return array<int, SlowTest>
+     */
+    public function collected(): array
+    {
+        return \array_values($this->slowTests);
+    }
+
+    private static function key(Event\Code\Test $test): string
+    {
+        return \sprintf(
+            '%s::%s',
+            $test->className(),
+            $test->methodNameWithDataSet(),
+        );
+    }
+}
diff --git a/src/SlowTestCollector.php b/src/SlowTestCollector.php
index d322e0bb..32c285c6 100644
--- a/src/SlowTestCollector.php
+++ b/src/SlowTestCollector.php
@@ -17,19 +17,20 @@
 
 final class SlowTestCollector
 {
-    private TimeKeeper $timer;
-
     private Event\Telemetry\Duration $maximumDuration;
 
-    /**
-     * @var array<string, SlowTest>
-     */
-    private array $slowTests = [];
+    private TimeKeeper $timer;
 
-    public function __construct(TimeKeeper $timeKeeper, Event\Telemetry\Duration $maximumDuration)
-    {
-        $this->timer = $timeKeeper;
+    private Collector $collector;
+
+    public function __construct(
+        Event\Telemetry\Duration $maximumDuration,
+        TimeKeeper $timeKeeper,
+        Collector $collector
+    ) {
         $this->maximumDuration = $maximumDuration;
+        $this->timer = $timeKeeper;
+        $this->collector = $collector;
     }
 
     public function testPrepared(Event\Code\Test $test, Event\Telemetry\HRTime $preparedTime): void
@@ -56,21 +57,7 @@ public function testPassed(Event\Code\Test $test, Event\Telemetry\HRTime $passed
             $duration
         );
 
-        $key = self::key($test);
-
-        if (\array_key_exists($key, $this->slowTests)) {
-            $previousSlowTest = $this->slowTests[$key];
-
-            if (!$duration->isGreaterThan($previousSlowTest->duration())) {
-                return;
-            }
-
-            $this->slowTests[$key] = $slowTest;
-
-            return;
-        }
-
-        $this->slowTests[$key] = $slowTest;
+        $this->collector->collect($slowTest);
     }
 
     public function maximumDuration(): Event\Telemetry\Duration
@@ -86,15 +73,6 @@ public function maximumDuration(): Event\Telemetry\Duration
      */
     public function slowTests(): array
     {
-        return \array_values($this->slowTests);
-    }
-
-    private static function key(Event\Code\Test $test): string
-    {
-        return \sprintf(
-            '%s::%s',
-            $test->className(),
-            $test->methodNameWithDataSet(),
-        );
+        return $this->collector->collected();
     }
 }
diff --git a/test/Unit/CollectorTest.php b/test/Unit/CollectorTest.php
new file mode 100644
index 00000000..8bcee465
--- /dev/null
+++ b/test/Unit/CollectorTest.php
@@ -0,0 +1,203 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright (c) 2021 Andreas Möller
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE.md file that was distributed with this source code.
+ *
+ * @see https://github.com/ergebnis/phpunit-slow-test-detector
+ */
+
+namespace Ergebnis\PHPUnit\SlowTestDetector\Test\Unit;
+
+use Ergebnis\PHPUnit\SlowTestDetector\Collector;
+use Ergebnis\PHPUnit\SlowTestDetector\SlowTest;
+use Ergebnis\PHPUnit\SlowTestDetector\Test\Fixture;
+use Ergebnis\Test\Util;
+use PHPUnit\Event;
+use PHPUnit\Framework;
+
+/**
+ * @internal
+ *
+ * @covers \Ergebnis\PHPUnit\SlowTestDetector\Collector
+ *
+ * @uses \Ergebnis\PHPUnit\SlowTestDetector\SlowTest
+ */
+final class CollectorTest extends Framework\TestCase
+{
+    use Util\Helper;
+
+    public function testDefaults(): void
+    {
+        $collector = new Collector();
+
+        self::assertSame([], $collector->collected());
+    }
+
+    public function testCollectCollectsSlowTests(): void
+    {
+        $faker = self::faker();
+
+        $first = SlowTest::fromTestAndDuration(
+            new Event\Code\Test(
+                Fixture\ExampleTest::class,
+                'foo',
+                'foo with data set #123',
+            ),
+            Event\Telemetry\Duration::fromSecondsAndNanoseconds(
+                $faker->numberBetween(),
+                $faker->numberBetween(0, 999_999_999)
+            )
+        );
+
+        $second = SlowTest::fromTestAndDuration(
+            new Event\Code\Test(
+                Fixture\ExampleTest::class,
+                'bar',
+                'bar',
+            ),
+            Event\Telemetry\Duration::fromSecondsAndNanoseconds(
+                $faker->numberBetween(),
+                $faker->numberBetween(0, 999_999_999)
+            )
+        );
+
+        $third = SlowTest::fromTestAndDuration(
+            new Event\Code\Test(
+                Fixture\ExampleTest::class,
+                'baz',
+                'baz with data set "string"',
+            ),
+            Event\Telemetry\Duration::fromSecondsAndNanoseconds(
+                $faker->numberBetween(),
+                $faker->numberBetween(0, 999_999_999)
+            )
+        );
+
+        $collector = new Collector();
+
+        $collector->collect($first);
+        $collector->collect($second);
+        $collector->collect($third);
+
+        $expected = [
+            $first,
+            $second,
+            $third,
+        ];
+
+        self::assertSame($expected, $collector->collected());
+    }
+
+    public function testCollectDoesNotReplaceSlowTestWhenDurationIsLessThanPreviousSlowTest(): void
+    {
+        $faker = self::faker();
+
+        $first = SlowTest::fromTestAndDuration(
+            new Event\Code\Test(
+                Fixture\ExampleTest::class,
+                'foo',
+                'foo with data set #123',
+            ),
+            Event\Telemetry\Duration::fromSecondsAndNanoseconds(
+                $faker->numberBetween(1),
+                $faker->numberBetween(0, 999_999_999)
+            )
+        );
+
+        $second = SlowTest::fromTestAndDuration(
+            new Event\Code\Test(
+                Fixture\ExampleTest::class,
+                'bar',
+                'bar',
+            ),
+            Event\Telemetry\Duration::fromSecondsAndNanoseconds(
+                $faker->numberBetween(),
+                $faker->numberBetween(0, 999_999_999)
+            )
+        );
+
+        $thirdForSameTest = SlowTest::fromTestAndDuration(
+            new Event\Code\Test(
+                $first->test()->className(),
+                $first->test()->methodName(),
+                $first->test()->methodNameWithDataSet(),
+            ),
+            Event\Telemetry\Duration::fromSecondsAndNanoseconds(
+                $faker->numberBetween(0, $first->duration()->seconds() - 1),
+                $faker->numberBetween(0, 999_999_999)
+            )
+        );
+
+        $collector = new Collector();
+
+        $collector->collect($first);
+        $collector->collect($second);
+        $collector->collect($thirdForSameTest);
+
+        $expected = [
+            $first,
+            $second,
+        ];
+
+        self::assertSame($expected, $collector->collected());
+    }
+
+    public function testCollectReplacesSlowTestWhenDurationIsGreaterThanPreviousSlowTest(): void
+    {
+        $faker = self::faker();
+
+        $first = SlowTest::fromTestAndDuration(
+            new Event\Code\Test(
+                Fixture\ExampleTest::class,
+                'foo',
+                'foo with data set #123',
+            ),
+            Event\Telemetry\Duration::fromSecondsAndNanoseconds(
+                $faker->numberBetween(),
+                $faker->numberBetween(0, 999_999_999)
+            )
+        );
+
+        $second = SlowTest::fromTestAndDuration(
+            new Event\Code\Test(
+                Fixture\ExampleTest::class,
+                'bar',
+                'bar',
+            ),
+            Event\Telemetry\Duration::fromSecondsAndNanoseconds(
+                $faker->numberBetween(),
+                $faker->numberBetween(0, 999_999_999)
+            )
+        );
+
+        $thirdForSameTest = SlowTest::fromTestAndDuration(
+            new Event\Code\Test(
+                $first->test()->className(),
+                $first->test()->methodName(),
+                $first->test()->methodNameWithDataSet(),
+            ),
+            Event\Telemetry\Duration::fromSecondsAndNanoseconds(
+                $faker->numberBetween($first->duration()->seconds() + 1),
+                $faker->numberBetween(0, 999_999_999)
+            )
+        );
+
+        $collector = new Collector();
+
+        $collector->collect($first);
+        $collector->collect($second);
+        $collector->collect($thirdForSameTest);
+
+        $expected = [
+            $thirdForSameTest,
+            $second,
+        ];
+
+        self::assertSame($expected, $collector->collected());
+    }
+}
diff --git a/test/Unit/SlowTestCollectorTest.php b/test/Unit/SlowTestCollectorTest.php
index b2950061..2f623cde 100644
--- a/test/Unit/SlowTestCollectorTest.php
+++ b/test/Unit/SlowTestCollectorTest.php
@@ -13,6 +13,7 @@
 
 namespace Ergebnis\PHPUnit\SlowTestDetector\Test\Unit;
 
+use Ergebnis\PHPUnit\SlowTestDetector\Collector;
 use Ergebnis\PHPUnit\SlowTestDetector\SlowTest;
 use Ergebnis\PHPUnit\SlowTestDetector\SlowTestCollector;
 use Ergebnis\PHPUnit\SlowTestDetector\TimeKeeper;
@@ -25,6 +26,7 @@
  *
  * @covers \Ergebnis\PHPUnit\SlowTestDetector\SlowTestCollector
  *
+ * @uses \Ergebnis\PHPUnit\SlowTestDetector\Collector
  * @uses \Ergebnis\PHPUnit\SlowTestDetector\SlowTest
  * @uses \Ergebnis\PHPUnit\SlowTestDetector\TimeKeeper
  */
@@ -37,8 +39,9 @@ public function testDefaults(): void
         $maximumDuration = Event\Telemetry\Duration::fromSeconds(self::faker()->numberBetween());
 
         $slowTestCollector = new SlowTestCollector(
+            $maximumDuration,
             new TimeKeeper(),
-            $maximumDuration
+            new Collector()
         );
 
         self::assertSame([], $slowTestCollector->slowTests());
@@ -49,8 +52,9 @@ public function testConstructorSetsValues(): void
         $maximumDuration = Event\Telemetry\Duration::fromSeconds(self::faker()->numberBetween());
 
         $slowTestCollector = new SlowTestCollector(
+            $maximumDuration,
             new TimeKeeper(),
-            $maximumDuration
+            new Collector()
         );
 
         self::assertSame($maximumDuration, $slowTestCollector->maximumDuration());
@@ -73,8 +77,9 @@ public function testDoesNotCollectSlowTestWhenTestHasBeenPreparedButHasNotPassed
         );
 
         $slowTestCollector = new SlowTestCollector(
+            $maximumDuration,
             new TimeKeeper(),
-            $maximumDuration
+            new Collector()
         );
 
         $slowTestCollector->testPrepared(
@@ -102,8 +107,9 @@ public function testDoesNotCollectSlowTestWhenTestHasPassedButNotBeenPrepared():
         );
 
         $slowTestCollector = new SlowTestCollector(
+            $maximumDuration,
             new TimeKeeper(),
-            $maximumDuration
+            new Collector()
         );
 
         $slowTestCollector->testPassed(
@@ -138,8 +144,9 @@ public function testDoesNotCollectSlowTestWhenTestHasBeenPreparedAndPassedWithDu
         );
 
         $slowTestCollector = new SlowTestCollector(
+            $maximumDuration,
             new TimeKeeper(),
-            $maximumDuration
+            new Collector()
         );
 
         $slowTestCollector->testPrepared(
@@ -179,8 +186,9 @@ public function testDoesNotCollectSlowTestWhenTestHasBeenPreparedAndPassedWithDu
         );
 
         $slowTestCollector = new SlowTestCollector(
+            $maximumDuration,
             new TimeKeeper(),
-            $maximumDuration
+            new Collector()
         );
 
         $slowTestCollector->testPrepared(
@@ -220,8 +228,9 @@ public function testCollectsSlowTestWhenTestHasBeenPreparedAndPassedWithDuration
         );
 
         $slowTestCollector = new SlowTestCollector(
+            $maximumDuration,
             new TimeKeeper(),
-            $maximumDuration
+            new Collector()
         );
 
         $slowTestCollector->testPrepared(
@@ -282,8 +291,9 @@ public function testDoesNotReplaceSlowTestWhenDurationIsGreaterThanMaximumDurati
         );
 
         $slowTestCollector = new SlowTestCollector(
+            $maximumDuration,
             new TimeKeeper(),
-            $maximumDuration
+            new Collector()
         );
 
         $slowTestCollector->testPrepared(
@@ -347,8 +357,9 @@ public function testDoesNotReplaceSlowTestWhenDurationIsGreaterThanMaximumDurati
         );
 
         $slowTestCollector = new SlowTestCollector(
+            $maximumDuration,
             new TimeKeeper(),
-            $maximumDuration
+            new Collector()
         );
 
         $slowTestCollector->testPrepared(
@@ -414,8 +425,9 @@ public function testReplacesSlowTestWhenDurationIsGreaterThanMaximumDurationAndG
         );
 
         $slowTestCollector = new SlowTestCollector(
+            $maximumDuration,
             new TimeKeeper(),
-            $maximumDuration
+            new Collector()
         );
 
         $slowTestCollector->testPrepared(
@@ -528,8 +540,9 @@ public function testCollectsMultipleSlowTestsWhenDurationIsGreaterThanMaximumDur
         );
 
         $slowTestCollector = new SlowTestCollector(
+            $maximumDuration,
             new TimeKeeper(),
-            $maximumDuration
+            new Collector()
         );
 
         $slowTestCollector->testPrepared(
diff --git a/test/Unit/Subscriber/TestPassedSubscriberTest.php b/test/Unit/Subscriber/TestPassedSubscriberTest.php
index 8934561b..a92e0c65 100644
--- a/test/Unit/Subscriber/TestPassedSubscriberTest.php
+++ b/test/Unit/Subscriber/TestPassedSubscriberTest.php
@@ -13,6 +13,7 @@
 
 namespace Ergebnis\PHPUnit\SlowTestDetector\Test\Unit\Subscriber;
 
+use Ergebnis\PHPUnit\SlowTestDetector\Collector;
 use Ergebnis\PHPUnit\SlowTestDetector\SlowTest;
 use Ergebnis\PHPUnit\SlowTestDetector\SlowTestCollector;
 use Ergebnis\PHPUnit\SlowTestDetector\Subscriber\TestPassedSubscriber;
@@ -26,6 +27,7 @@
  *
  * @covers \Ergebnis\PHPUnit\SlowTestDetector\Subscriber\TestPassedSubscriber
  *
+ * @uses \Ergebnis\PHPUnit\SlowTestDetector\Collector
  * @uses \Ergebnis\PHPUnit\SlowTestDetector\SlowTest
  * @uses \Ergebnis\PHPUnit\SlowTestDetector\SlowTestCollector
  * @uses \Ergebnis\PHPUnit\SlowTestDetector\TimeKeeper
@@ -38,8 +40,6 @@ public function testNotifyCollectsPreparedTest(): void
     {
         $faker = self::faker();
 
-        $timeKeeper = new TimeKeeper();
-
         $maximumDuration = Event\Telemetry\Duration::fromSeconds($faker->numberBetween(
             5,
             10
@@ -65,8 +65,9 @@ public function testNotifyCollectsPreparedTest(): void
         );
 
         $slowTestCollector = new SlowTestCollector(
-            $timeKeeper,
-            $maximumDuration
+            $maximumDuration,
+            new TimeKeeper(),
+            new Collector()
         );
 
         $slowTestCollector->testPrepared(
diff --git a/test/Unit/Subscriber/TestPreparedSubscriberTest.php b/test/Unit/Subscriber/TestPreparedSubscriberTest.php
index 5fac7cb4..b0b4538c 100644
--- a/test/Unit/Subscriber/TestPreparedSubscriberTest.php
+++ b/test/Unit/Subscriber/TestPreparedSubscriberTest.php
@@ -13,6 +13,7 @@
 
 namespace Ergebnis\PHPUnit\SlowTestDetector\Test\Unit\Subscriber;
 
+use Ergebnis\PHPUnit\SlowTestDetector\Collector;
 use Ergebnis\PHPUnit\SlowTestDetector\SlowTest;
 use Ergebnis\PHPUnit\SlowTestDetector\SlowTestCollector;
 use Ergebnis\PHPUnit\SlowTestDetector\Subscriber\TestPreparedSubscriber;
@@ -26,6 +27,7 @@
  *
  * @covers \Ergebnis\PHPUnit\SlowTestDetector\Subscriber\TestPreparedSubscriber
  *
+ * @uses \Ergebnis\PHPUnit\SlowTestDetector\Collector
  * @uses \Ergebnis\PHPUnit\SlowTestDetector\SlowTest
  * @uses \Ergebnis\PHPUnit\SlowTestDetector\SlowTestCollector
  * @uses \Ergebnis\PHPUnit\SlowTestDetector\TimeKeeper
@@ -38,8 +40,6 @@ public function testNotifyCollectsPreparedTest(): void
     {
         $faker = self::faker();
 
-        $timeKeeper = new TimeKeeper();
-
         $maximumDuration = Event\Telemetry\Duration::fromSeconds($faker->numberBetween(
             5,
             10
@@ -65,8 +65,9 @@ public function testNotifyCollectsPreparedTest(): void
         $passedTest = clone $preparedTest;
 
         $slowTestCollector = new SlowTestCollector(
-            $timeKeeper,
-            $maximumDuration
+            $maximumDuration,
+            new TimeKeeper(),
+            new Collector()
         );
 
         $subscriber = new TestPreparedSubscriber($slowTestCollector);