diff --git a/test/EventSnapshotsTest.php b/test/EventSnapshotsTest.php
new file mode 100644
index 0000000..82df738
--- /dev/null
+++ b/test/EventSnapshotsTest.php
@@ -0,0 +1,173 @@
+<?php
+
+namespace PostHog\Test;
+
+use PostHog\Client;
+use PostHog\PostHog;
+use Symfony\Component\Clock\Clock;
+use Symfony\Component\Clock\MockClock;
+use Symfony\Component\Clock\NativeClock;
+
+class EventSnapshotsTest extends JsonSnapshotTestCase
+{
+    private const API_KEY = 'phc_snapshot_project_key';
+
+    private MockedHttpClient $httpClient;
+    private Client $client;
+
+    protected function setUp(): void
+    {
+        date_default_timezone_set('UTC');
+        Clock::set(new MockClock(new \DateTimeImmutable('2024-01-02T03:04:05.123456+00:00')));
+        $this->httpClient = new MockedHttpClient('snapshot.posthog.test');
+        $this->client = new Client(
+            self::API_KEY,
+            [
+                'batch_size' => 100,
+                'debug' => true,
+            ],
+            $this->httpClient,
+            null,
+            false
+        );
+        PostHog::init(null, null, $this->client);
+    }
+
+    protected function tearDown(): void
+    {
+        $this->client->shutdown();
+        Clock::set(new NativeClock());
+    }
+
+    public function testEventFamilyBatchRequestMatchesSnapshot(): void
+    {
+        self::assertTrue($this->client->capture([
+            'distinctId' => 'person-123',
+            'event' => 'checkout completed',
+            'groups' => [
+                'organization' => 'org-42',
+                'project' => 'project-7',
+            ],
+            'properties' => [
+                'boolean_false' => false,
+                'boolean_true' => true,
+                'empty_list' => [],
+                'empty_object' => (object) [],
+                'empty_string' => '',
+                'float' => 42.5,
+                'floating_zero' => 0.0,
+                'integer' => 42,
+                'large_integer' => 9007199254740991,
+                'negative_floating_zero' => -0.0,
+                'negative_integer' => -42,
+                'list_order' => ['third', 'first', 'second'],
+                'nested_object' => [
+                    'zeta' => null,
+                    'alpha' => 'first',
+                ],
+                'null' => null,
+                'numeric_string' => '0',
+                'text' => "line one\n\"quoted\" \\ slash / café 🌍",
+                'zero' => 0,
+            ],
+        ]));
+
+        self::assertTrue($this->client->identify([
+            'distinctId' => 'person-123',
+            'properties' => [
+                'email' => 'person@example.com',
+                'roles' => ['admin', 'editor'],
+                'preferences' => (object) [],
+            ],
+        ]));
+
+        self::assertTrue($this->client->alias([
+            'distinctId' => 'person-123',
+            'alias' => 'anonymous-456',
+            'properties' => [
+                'source' => 'snapshot-suite',
+            ],
+        ]));
+
+        self::assertTrue(PostHog::groupIdentify([
+            'groupType' => 'organization',
+            'groupKey' => 'org-42',
+            'properties' => [
+                'employees' => 150,
+                'labels' => ['customer', 'beta'],
+                'metadata' => (object) [],
+                'name' => 'PostHog',
+            ],
+        ]));
+
+        self::assertTrue($this->client->flush());
+        self::assertCount(1, $this->httpClient->calls);
+
+        $this->assertJsonSnapshot(
+            'event-family-request.json',
+            $this->structuredRequest($this->httpClient->calls[0])
+        );
+    }
+
+    public function testCompleteFlagsRequestMatchesSnapshot(): void
+    {
+        $this->client->flags(
+            'person-123',
+            [
+                'organization' => 'org-42',
+                'project' => 'project-7',
+            ],
+            [
+                'empty_list' => [],
+                'empty_object' => (object) [],
+                'nullable' => null,
+                'plan' => 'enterprise',
+                'roles' => ['admin', 'editor'],
+            ],
+            [
+                'organization' => [
+                    'employee_count' => 150,
+                    'industry' => 'analytics',
+                    'settings' => (object) [],
+                ],
+                'project' => [
+                    'enabled' => false,
+                    'tags' => ['php', 'server'],
+                ],
+            ],
+            true,
+            ['checkout-redesign', 'server-rollout']
+        );
+
+        self::assertCount(1, $this->httpClient->calls);
+        $this->assertJsonSnapshot(
+            'flags-request.json',
+            $this->structuredRequest($this->httpClient->calls[0])
+        );
+    }
+
+    /**
+     * @param array{
+     *     path: string,
+     *     payload: string,
+     *     extraHeaders: array<int, string>,
+     *     requestOptions: array<string, mixed>
+     * } $call
+     * @return array<string, mixed>
+     */
+    private function structuredRequest(array $call): array
+    {
+        $headers = [];
+        foreach ($call['extraHeaders'] as $header) {
+            [$name, $value] = explode(':', $header, 2);
+            $headers[trim($name)] = trim($value);
+        }
+
+        return [
+            'body' => json_decode($call['payload'], false, 512, JSON_THROW_ON_ERROR),
+            'headers' => $headers,
+            'options' => $call['requestOptions'],
+            'path' => $call['path'],
+        ];
+    }
+}
diff --git a/test/JsonSnapshotTestCase.php b/test/JsonSnapshotTestCase.php
new file mode 100644
index 0000000..ce487a0
--- /dev/null
+++ b/test/JsonSnapshotTestCase.php
@@ -0,0 +1,100 @@
+<?php
+
+namespace PostHog\Test;
+
+use PHPUnit\Framework\TestCase;
+use stdClass;
+
+abstract class JsonSnapshotTestCase extends TestCase
+{
+    /** @var array<string, string> */
+    private array $uuidPlaceholders = [];
+
+    protected function assertJsonSnapshot(string $name, mixed $actual): void
+    {
+        $this->uuidPlaceholders = [];
+        $normalized = $this->normalizeValue($actual);
+        $rendered = json_encode(
+            $normalized,
+            JSON_PRETTY_PRINT
+                | JSON_UNESCAPED_SLASHES
+                | JSON_UNESCAPED_UNICODE
+                | JSON_PRESERVE_ZERO_FRACTION
+                | JSON_THROW_ON_ERROR
+        ) . "\n";
+        $path = __DIR__ . '/assests/snapshots/' . $name;
+
+        if (getenv('UPDATE_EVENT_SHAPE_SNAPSHOTS') === '1') {
+            file_put_contents($path, $rendered);
+        }
+
+        self::assertFileExists($path, "Missing snapshot {$name}");
+        self::assertSame(
+            file_get_contents($path),
+            $rendered,
+            "Snapshot {$name} changed. Re-record with UPDATE_EVENT_SHAPE_SNAPSHOTS=1."
+        );
+    }
+
+    private function normalizeValue(mixed $value, ?string $key = null): mixed
+    {
+        if ($key === 'api_key' || $key === 'personal_api_key' || $key === 'secret_key') {
+            return '<redacted>';
+        }
+
+        if ($key === '$lib_version') {
+            return '<sdk-version>';
+        }
+
+        if (is_string($value)) {
+            if (preg_match('/^posthog-php\/.+$/', $value) === 1) {
+                return 'posthog-php/<sdk-version>';
+            }
+
+            if ($this->isUuid($value)) {
+                if (!isset($this->uuidPlaceholders[$value])) {
+                    $this->uuidPlaceholders[$value] = '<uuid-' . (count($this->uuidPlaceholders) + 1) . '>';
+                }
+
+                return $this->uuidPlaceholders[$value];
+            }
+
+            return $value;
+        }
+
+        if ($value instanceof stdClass) {
+            $properties = get_object_vars($value);
+            ksort($properties, SORT_STRING);
+            $normalized = new stdClass();
+            foreach ($properties as $property => $propertyValue) {
+                $normalized->{$property} = $this->normalizeValue($propertyValue, $property);
+            }
+
+            return $normalized;
+        }
+
+        if (is_array($value)) {
+            if (array_is_list($value)) {
+                return array_map(fn(mixed $item): mixed => $this->normalizeValue($item), $value);
+            }
+
+            ksort($value, SORT_STRING);
+            $normalized = [];
+            foreach ($value as $property => $propertyValue) {
+                $normalized[$property] = $this->normalizeValue($propertyValue, (string) $property);
+            }
+
+            return $normalized;
+        }
+
+        return $value;
+    }
+
+    private function isUuid(string $value): bool
+    {
+        return preg_match(
+            '/^[0-9a-f]{8}-[0-9a-f]{4}-[1-8][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i',
+            $value
+        ) === 1;
+    }
+}
diff --git a/test/assests/snapshots/event-family-request.json b/test/assests/snapshots/event-family-request.json
new file mode 100644
index 0000000..64b593b
--- /dev/null
+++ b/test/assests/snapshots/event-family-request.json
@@ -0,0 +1,127 @@
+{
+    "body": {
+        "api_key": "<redacted>",
+        "batch": [
+            {
+                "$groups": {
+                    "organization": "org-42",
+                    "project": "project-7"
+                },
+                "distinct_id": "person-123",
+                "event": "checkout completed",
+                "groups": {
+                    "organization": "org-42",
+                    "project": "project-7"
+                },
+                "properties": {
+                    "$groups": {
+                        "organization": "org-42",
+                        "project": "project-7"
+                    },
+                    "$is_server": true,
+                    "$lib": "posthog-php",
+                    "$lib_consumer": "LibCurl",
+                    "$lib_version": "<sdk-version>",
+                    "boolean_false": false,
+                    "boolean_true": true,
+                    "empty_list": [],
+                    "empty_object": {},
+                    "empty_string": "",
+                    "float": 42.5,
+                    "floating_zero": 0,
+                    "integer": 42,
+                    "large_integer": 9007199254740991,
+                    "list_order": [
+                        "third",
+                        "first",
+                        "second"
+                    ],
+                    "negative_floating_zero": 0,
+                    "negative_integer": -42,
+                    "nested_object": {
+                        "alpha": "first",
+                        "zeta": null
+                    },
+                    "null": null,
+                    "numeric_string": "0",
+                    "text": "line one\n\"quoted\" \\ slash / café 🌍",
+                    "zero": 0
+                },
+                "timestamp": "2024-01-02T03:04:05.123456+00:00",
+                "uuid": "<uuid-1>"
+            },
+            {
+                "$set": {
+                    "email": "person@example.com",
+                    "preferences": {},
+                    "roles": [
+                        "admin",
+                        "editor"
+                    ]
+                },
+                "distinct_id": "person-123",
+                "event": "$identify",
+                "groups": [],
+                "properties": {
+                    "$is_server": true,
+                    "$lib": "posthog-php",
+                    "$lib_consumer": "LibCurl",
+                    "$lib_version": "<sdk-version>",
+                    "email": "person@example.com",
+                    "preferences": {},
+                    "roles": [
+                        "admin",
+                        "editor"
+                    ]
+                },
+                "timestamp": "2024-01-02T03:04:05.123456+00:00"
+            },
+            {
+                "distinct_id": null,
+                "event": "$create_alias",
+                "groups": [],
+                "properties": {
+                    "$is_server": true,
+                    "$lib": "posthog-php",
+                    "$lib_consumer": "LibCurl",
+                    "$lib_version": "<sdk-version>",
+                    "alias": "anonymous-456",
+                    "distinct_id": "person-123",
+                    "source": "snapshot-suite"
+                },
+                "timestamp": "2024-01-02T03:04:05.123456+00:00"
+            },
+            {
+                "distinct_id": "$organization_org-42",
+                "event": "$groupidentify",
+                "groups": [],
+                "properties": {
+                    "$group_key": "org-42",
+                    "$group_set": {
+                        "employees": 150,
+                        "labels": [
+                            "customer",
+                            "beta"
+                        ],
+                        "metadata": {},
+                        "name": "PostHog"
+                    },
+                    "$group_type": "organization",
+                    "$is_server": true,
+                    "$lib": "posthog-php",
+                    "$lib_consumer": "LibCurl",
+                    "$lib_version": "<sdk-version>"
+                },
+                "timestamp": "2024-01-02T03:04:05.123456+00:00",
+                "uuid": "<uuid-2>"
+            }
+        ]
+    },
+    "headers": {
+        "User-Agent": "posthog-php/<sdk-version>"
+    },
+    "options": {
+        "shouldVerify": true
+    },
+    "path": "/batch/"
+}
diff --git a/test/assests/snapshots/flags-request.json b/test/assests/snapshots/flags-request.json
new file mode 100644
index 0000000..1e0dcb3
--- /dev/null
+++ b/test/assests/snapshots/flags-request.json
@@ -0,0 +1,47 @@
+{
+    "body": {
+        "api_key": "<redacted>",
+        "distinct_id": "person-123",
+        "flag_keys_to_evaluate": [
+            "checkout-redesign",
+            "server-rollout"
+        ],
+        "geoip_disable": true,
+        "group_properties": {
+            "organization": {
+                "employee_count": 150,
+                "industry": "analytics",
+                "settings": {}
+            },
+            "project": {
+                "enabled": false,
+                "tags": [
+                    "php",
+                    "server"
+                ]
+            }
+        },
+        "groups": {
+            "organization": "org-42",
+            "project": "project-7"
+        },
+        "person_properties": {
+            "empty_list": [],
+            "empty_object": {},
+            "nullable": null,
+            "plan": "enterprise",
+            "roles": [
+                "admin",
+                "editor"
+            ]
+        }
+    },
+    "headers": {
+        "User-Agent": "posthog-php/<sdk-version>"
+    },
+    "options": {
+        "shouldRetry": false,
+        "timeout": 3000
+    },
+    "path": "/flags/?v=2"
+}