diff --git a/psalm-baseline.xml b/psalm-baseline.xml
index ff5e8e09..a5ca33e8 100644
--- a/psalm-baseline.xml
+++ b/psalm-baseline.xml
@@ -36,9 +36,9 @@
     </NonInvariantDocblockPropertyType>
   </file>
   <file src="src/BaseInputFilter.php">
-    <DocblockTypeContradiction occurrences="1">
-      <code>! is_string($name)</code>
-    </DocblockTypeContradiction>
+    <InvalidPropertyAssignmentValue occurrences="1">
+      <code>$this-&gt;inputs</code>
+    </InvalidPropertyAssignmentValue>
     <InvalidReturnStatement occurrences="1">
       <code>$messages</code>
     </InvalidReturnStatement>
diff --git a/src/BaseInputFilter.php b/src/BaseInputFilter.php
index e2cde53a..a163eaa2 100644
--- a/src/BaseInputFilter.php
+++ b/src/BaseInputFilter.php
@@ -23,7 +23,6 @@
 use function is_array;
 use function is_int;
 use function is_object;
-use function is_string;
 use function sprintf;
 
 class BaseInputFilter implements
@@ -499,7 +498,7 @@ public function getMessages()
     protected function validateValidationGroup(array $inputs)
     {
         foreach ($inputs as $name) {
-            if (! is_string($name) || ! array_key_exists($name, $this->inputs)) {
+            if (! array_key_exists($name, $this->inputs)) {
                 throw new Exception\InvalidArgumentException(sprintf(
                     'setValidationGroup() expects a list of valid input names; "%s" was not found',
                     (string) $name
diff --git a/test/ValidationGroup/InputFilterCollectionsValidationGroupTest.php b/test/ValidationGroup/InputFilterCollectionsValidationGroupTest.php
new file mode 100644
index 00000000..181d8094
--- /dev/null
+++ b/test/ValidationGroup/InputFilterCollectionsValidationGroupTest.php
@@ -0,0 +1,213 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LaminasTest\InputFilter\ValidationGroup;
+
+use Laminas\InputFilter\CollectionInputFilter;
+use Laminas\InputFilter\Input;
+use Laminas\InputFilter\InputFilter;
+use PHPUnit\Framework\TestCase;
+
+use const PHP_VERSION_ID;
+
+final class InputFilterCollectionsValidationGroupTest extends TestCase
+{
+    private InputFilter $inputFilter;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $collection = new CollectionInputFilter();
+        $collection->setIsRequired(true);
+
+        $first = new Input('first');
+        $first->setRequired(true);
+        $second = new Input('second');
+        $second->setRequired(true);
+
+        $nestedFilter = new InputFilter();
+        $nestedFilter->add($first);
+        $nestedFilter->add($second);
+        $collection->setInputFilter($nestedFilter);
+
+        $this->inputFilter = new InputFilter();
+        $this->inputFilter->add($collection, 'stuff');
+    }
+
+    /** @return array<string, array{0: int|null}> */
+    public function collectionCountProvider(): array
+    {
+        return [
+            'Collection Count: None'  => [null],
+            'Collection Count: One'   => [1],
+            'Collection Count: Two'   => [2],
+            'Collection Count: Three' => [3],
+            'Collection Count: Four'  => [4],
+        ];
+    }
+
+    private function setCollectionCount(?int $count): void
+    {
+        if ($count === null) {
+            return;
+        }
+
+        $collection = $this->inputFilter->get('stuff');
+        self::assertInstanceOf(CollectionInputFilter::class, $collection);
+        $collection->setCount($count);
+    }
+
+    /** @dataProvider collectionCountProvider */
+    public function testIncompleteDataFailsValidation(?int $count): void
+    {
+        $this->setCollectionCount($count);
+        $this->inputFilter->setData([
+            'stuff' => [
+                ['first' => 'Foo'],
+            ],
+        ]);
+        self::assertFalse($this->inputFilter->isValid());
+    }
+
+    /** @dataProvider collectionCountProvider */
+    public function testCompleteDataPassesValidation(?int $count): void
+    {
+        $this->setCollectionCount($count);
+        $this->inputFilter->setData([
+            'stuff' => [
+                ['first' => 'Foo', 'second' => 'Bar'],
+                ['first' => 'Foo', 'second' => 'Bar'],
+                ['first' => 'Foo', 'second' => 'Bar'],
+                ['first' => 'Foo', 'second' => 'Bar'],
+            ],
+        ]);
+
+        self::assertTrue($this->inputFilter->isValid());
+    }
+
+    /** @dataProvider collectionCountProvider */
+    public function testValidationFailsForCollectionItemValidity(?int $count): void
+    {
+        $this->setCollectionCount($count);
+        $this->inputFilter->setData([
+            'stuff' => [
+                ['first' => 'Foo', 'second' => 'Bar'],
+                ['first' => '', 'second' => 'Bar'],
+                ['first' => 'Foo', 'second' => ''],
+                ['first' => '', 'second' => ''],
+            ],
+        ]);
+
+        self::assertFalse($this->inputFilter->isValid());
+    }
+
+    /** @dataProvider collectionCountProvider */
+    public function testValidationGroupWithCollectionInputFilter(?int $count): void
+    {
+        $this->setCollectionCount($count);
+        $collection = $this->inputFilter->get('stuff');
+        self::assertInstanceOf(CollectionInputFilter::class, $collection);
+        $collection->getInputFilter()->setValidationGroup('first');
+
+        $this->inputFilter->setData([
+            'stuff' => [
+                ['first' => 'Foo'],
+                ['first' => 'Foo'],
+                ['first' => 'Foo'],
+                ['first' => 'Foo'],
+            ],
+        ]);
+
+        self::assertTrue($this->inputFilter->isValid());
+    }
+
+    /** @dataProvider collectionCountProvider */
+    public function testValidationGroupViaCollection(?int $count): void
+    {
+        $this->setCollectionCount($count);
+        $collection = $this->inputFilter->get('stuff');
+        self::assertInstanceOf(CollectionInputFilter::class, $collection);
+        /** @psalm-suppress InvalidArgument */
+        $collection->setValidationGroup([
+            0 => 'first',
+            1 => 'second',
+            2 => 'first',
+            3 => 'first',
+        ]);
+
+        $this->inputFilter->setData([
+            'stuff' => [
+                ['first' => 'Foo'],
+                ['second' => 'Foo'],
+                ['first' => 'Foo'],
+                ['first' => 'Foo'],
+            ],
+        ]);
+
+        self::assertTrue($this->inputFilter->isValid());
+    }
+
+    /**
+     * This test documents existing behaviour - the validation group must be set for elements 0 through 3
+     *
+     * @dataProvider collectionCountProvider
+     */
+    public function testValidationGroupViaCollectionMustSpecifyAllKeys(?int $count): void
+    {
+        $this->setCollectionCount($count);
+        $collection = $this->inputFilter->get('stuff');
+        self::assertInstanceOf(CollectionInputFilter::class, $collection);
+
+        /** @psalm-suppress InvalidArgument */
+        $collection->setValidationGroup([
+            0 => 'first',
+        ]);
+
+        $this->inputFilter->setData([
+            'stuff' => [
+                ['first' => 'Foo'],
+                ['first' => 'Foo'],
+                ['first' => 'Foo'],
+                ['first' => 'Foo'],
+            ],
+        ]);
+
+        if (PHP_VERSION_ID >= 80000) {
+            $this->expectWarning();
+            $this->expectWarningMessage('Undefined array key 1');
+        } else {
+            $this->expectNotice();
+            $this->expectNoticeMessage('Undefined offset: 1');
+        }
+
+        $this->inputFilter->isValid();
+    }
+
+    /** @dataProvider collectionCountProvider */
+    public function testValidationGroupViaTopLevelInputFilter(?int $count): void
+    {
+        $this->setCollectionCount($count);
+        /** @psalm-suppress InvalidArgument */
+        $this->inputFilter->setValidationGroup([
+            'stuff' => [
+                0 => 'first',
+                1 => 'second',
+                2 => 'first',
+                3 => 'first',
+            ],
+        ]);
+
+        $this->inputFilter->setData([
+            'stuff' => [
+                ['first' => 'Foo'],
+                ['second' => 'Foo'],
+                ['first' => 'Foo'],
+                ['first' => 'Foo'],
+            ],
+        ]);
+
+        self::assertTrue($this->inputFilter->isValid());
+    }
+}
diff --git a/test/ValidationGroup/InputFilterStringValidationGroupTest.php b/test/ValidationGroup/InputFilterStringValidationGroupTest.php
new file mode 100644
index 00000000..406ce14d
--- /dev/null
+++ b/test/ValidationGroup/InputFilterStringValidationGroupTest.php
@@ -0,0 +1,78 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LaminasTest\InputFilter\ValidationGroup;
+
+use Laminas\InputFilter\Exception\InvalidArgumentException;
+use Laminas\InputFilter\Input;
+use Laminas\InputFilter\InputFilter;
+use Laminas\Validator\StringLength;
+use PHPUnit\Framework\TestCase;
+
+final class InputFilterStringValidationGroupTest extends TestCase
+{
+    private InputFilter $inputFilter;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $first = new Input('first');
+        $first->setRequired(true);
+        $first->getValidatorChain()->attach(new StringLength(['min' => 5]));
+        $second = new Input('second');
+        $second->setRequired(true);
+        $second->getValidatorChain()->attach(new StringLength(['min' => 5]));
+        $third = new Input('third');
+        $third->setRequired(true);
+        $third->getValidatorChain()->attach(new StringLength(['min' => 5]));
+
+        $this->inputFilter = new InputFilter();
+        $this->inputFilter->add($first);
+        $this->inputFilter->add($second);
+        $this->inputFilter->add($third);
+    }
+
+    public function testValidationFailsForIncompleteInput(): void
+    {
+        $this->inputFilter->setData(['first' => 'Freddy']);
+        self::assertFalse($this->inputFilter->isValid());
+    }
+
+    public function testValidationSucceedsForCompleteInput(): void
+    {
+        $this->inputFilter->setData(['first' => 'Freddy', 'second' => 'Fruit Bat', 'third' => 'Muppet']);
+        self::assertTrue($this->inputFilter->isValid());
+    }
+
+    public function testValidationSucceedsForIncompleteInputWhenValidationGroupIsProvided(): void
+    {
+        $this->inputFilter->setValidationGroup('first');
+        $this->inputFilter->setData(['first' => 'Freddy']);
+
+        self::assertTrue($this->inputFilter->isValid());
+    }
+
+    public function testThatValidationGroupIsVariadic(): void
+    {
+        $this->inputFilter->setValidationGroup('first', 'second');
+        $this->inputFilter->setData(['first' => 'Freddy', 'second' => 'Fruit Bat']);
+
+        self::assertTrue($this->inputFilter->isValid());
+    }
+
+    public function testThatValidationGroupAcceptsListOfInputNames(): void
+    {
+        $this->inputFilter->setValidationGroup(['first', 'second']);
+        $this->inputFilter->setData(['first' => 'Freddy', 'second' => 'Fruit Bat']);
+
+        self::assertTrue($this->inputFilter->isValid());
+    }
+
+    public function testValidationGroupWithUnknownInput(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('"doughnuts" was not found');
+        $this->inputFilter->setValidationGroup(['doughnuts']);
+    }
+}