diff --git a/test/tests.js b/test/tests.js
index 798bb01..7e882d3 100644
--- a/test/tests.js
+++ b/test/tests.js
@@ -2,6 +2,7 @@ const assert = require('assert');
 const rimraf = require('rimraf');
 const path = require('path');
 const FetchCache = require('../index.js');
+const { URLSearchParams } = require('url');
 
 const CACHE_PATH = path.join(__dirname, '..', '.cache');
 
@@ -15,6 +16,10 @@ let fetch;
 let res;
 let body;
 
+function post(body) {
+  return { method: 'POST', body };
+}
+
 beforeEach(async function() {
   rimraf.sync(CACHE_PATH);
   fetch = FetchCache(CACHE_PATH);
@@ -104,6 +109,38 @@ describe('Cache tests', function() {
     await res.ejectFromCache();
     await res.ejectFromCache();
   });
+
+  it('Gives different string bodies different cache keys', async function() {
+    res = await fetch(TWO_HUNDRED_URL, post('a'));
+    assert.strictEqual(res.fromCache, false);
+
+    res = await fetch(TWO_HUNDRED_URL, post('b'));
+    assert.strictEqual(res.fromCache, false);
+  });
+
+  it('Gives same string bodies same cache keys', async function() {
+    res = await fetch(TWO_HUNDRED_URL, post('a'));
+    assert.strictEqual(res.fromCache, false);
+
+    res = await fetch(TWO_HUNDRED_URL, post('a'));
+    assert.strictEqual(res.fromCache, true);
+  });
+
+  it('Gives different URLSearchParams different cache keys', async function() {
+    res = await fetch(TWO_HUNDRED_URL, post(new URLSearchParams('a=a')));
+    assert.strictEqual(res.fromCache, false);
+
+    res = await fetch(TWO_HUNDRED_URL, post(new URLSearchParams('a=b')));
+    assert.strictEqual(res.fromCache, false);
+  });
+
+  it('Gives same URLSearchParams same cache keys', async function() {
+    res = await fetch(TWO_HUNDRED_URL, post(new URLSearchParams('a=a')));
+    assert.strictEqual(res.fromCache, false);
+
+    res = await fetch(TWO_HUNDRED_URL, post(new URLSearchParams('a=a')));
+    assert.strictEqual(res.fromCache, true);
+  });
 }).timeout(10000);
 
 describe('Data tests', function() {