diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 9464840..e4ad378 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -16,4 +16,4 @@ lint:
 
 test:
   stage: test
-  script: deno test
\ No newline at end of file
+  script: deno task test
\ No newline at end of file
diff --git a/deno.json b/deno.json
index b5508ad..d23bcde 100644
--- a/deno.json
+++ b/deno.json
@@ -1,5 +1,6 @@
 {
   "tasks": {
+    "test": "deno test --allow-read --allow-write"
   },
   "lint": {
     "files": {
diff --git a/src/deps.ts b/src/deps.ts
index 9403356..756bf2a 100644
--- a/src/deps.ts
+++ b/src/deps.ts
@@ -1,3 +1,3 @@
 export { readLines } from 'https://deno.land/std@0.181.0/io/mod.ts';
-export { assert } from 'https://deno.land/std@0.181.0/testing/asserts.ts';
+export { assert, assertEquals } from 'https://deno.land/std@0.181.0/testing/asserts.ts';
 export { Keydb } from 'https://deno.land/x/keydb@1.0.0/sqlite.ts';
diff --git a/src/policies/anti-duplication-policy.test.ts b/src/policies/anti-duplication-policy.test.ts
new file mode 100644
index 0000000..1e37f27
--- /dev/null
+++ b/src/policies/anti-duplication-policy.test.ts
@@ -0,0 +1,28 @@
+import { assertEquals } from '../deps.ts';
+import { buildEvent, buildInputMessage } from '../test.ts';
+
+import antiDuplicationPolicy from './anti-duplication-policy.ts';
+
+Deno.test({
+  name: 'blocks events that post the same content too quickly',
+  fn: async () => {
+    const content = 'Spicy peppermint apricot mediterranean ginger carrot spiced juice edamame hummus';
+
+    const opts = {
+      databaseUrl: `sqlite:///tmp/${crypto.randomUUID()}.sqlite3`,
+    };
+
+    const msg1 = buildInputMessage({ event: buildEvent({ content }) });
+
+    assertEquals((await antiDuplicationPolicy(msg1, opts)).action, 'accept');
+    assertEquals((await antiDuplicationPolicy(msg1, opts)).action, 'shadowReject');
+    assertEquals((await antiDuplicationPolicy(msg1, opts)).action, 'shadowReject');
+
+    const msg2 = buildInputMessage({ event: buildEvent({ content: 'a' }) });
+
+    assertEquals((await antiDuplicationPolicy(msg2, opts)).action, 'accept');
+    assertEquals((await antiDuplicationPolicy(msg2, opts)).action, 'accept');
+    assertEquals((await antiDuplicationPolicy(msg2, opts)).action, 'accept');
+  },
+  sanitizeResources: false,
+});