diff --git a/server.js b/server.js
index 636fc2ee62..5a2f3ba1b4 100644
--- a/server.js
+++ b/server.js
@@ -1254,6 +1254,15 @@ cache(function(data, match, sendBadge, request) {
     }
     try {
       var data = JSON.parse(buffer);
+      if (data.count.length === 0) {
+        /* Note the 'not found' response from libscore is:
+           status code = 200,
+           body = {"github":"","meta":{},"count":[],"sites":[]}
+        */
+        badgeData.text[1] = 'not found';
+        sendBadge(format, badgeData);
+        return;
+      }
       badgeData.text[1] = metric(+data.count[data.count.length-1]);
       badgeData.colorscheme = 'blue';
       sendBadge(format, badgeData);
diff --git a/services/libscore/libscore.tester.js b/services/libscore/libscore.tester.js
new file mode 100644
index 0000000000..67d4486d90
--- /dev/null
+++ b/services/libscore/libscore.tester.js
@@ -0,0 +1,41 @@
+'use strict';
+
+const Joi = require('joi');
+const ServiceTester = require('../service-tester');
+const { isMetric } = require('../test-validators');
+const { invalidJSON } = require('../response-fixtures');
+
+const t = new ServiceTester({ id: 'libscore', title: 'libscore' });
+module.exports = t;
+
+t.create('libscore (valid)')
+  .get('/s/jQuery.json')
+  .expectJSONTypes(Joi.object().keys({
+    name: 'libscore',
+    value: isMetric,
+  }));
+
+t.create('libscore (not found)')
+  .get('/s/not-a-library.json')
+  .expectJSON({name: 'libscore', value: 'not found'});
+
+t.create('libscore (connection error)')
+  .get('/s/jQuery.json')
+  .networkOff()
+  .expectJSON({name: 'libscore', value: 'inaccessible'});
+
+t.create('libscore (unexpected response)')
+  .get('/s/jQuery.json')
+  .intercept(nock => nock('http://api.libscore.com')
+    .get('/v1/libraries/jQuery')
+    .reply(invalidJSON)
+  )
+  .expectJSON({name: 'libscore', value: 'invalid'});
+
+t.create('libscore (error response)')
+  .get('/s/jQuery.json')
+  .intercept(nock => nock('http://api.libscore.com')
+    .get('/v1/libraries/jQuery')
+    .reply(500, '{"error":"oh noes!!"}')
+  )
+  .expectJSON({name: 'libscore', value: 'invalid'});