diff --git a/dangerfile.js b/dangerfile.js
index 148ea1c7c5..7966bf245f 100644
--- a/dangerfile.js
+++ b/dangerfile.js
@@ -7,6 +7,7 @@
 
 const { danger, fail, message, warn } = require('danger');
 const chainsmoker = require('chainsmoker');
+const { default: noTestShortcuts } = require('danger-plugin-no-test-shortcuts');
 
 const fileMatch = chainsmoker({
   created: danger.git.created_files,
@@ -140,3 +141,11 @@ affectedServices.forEach(function(service) {
     );
   }
 });
+
+// Prevent merging exclusive services tests.
+noTestShortcuts({
+  testFilePredicate: filePath => filePath.endsWith('.tester.js'),
+  patterns: {
+    only: ['only()'],
+  },
+});
diff --git a/package-lock.json b/package-lock.json
index 08022d73f1..57e99aa46d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -372,8 +372,7 @@
     "acorn": {
       "version": "2.7.0",
       "resolved": "https://registry.npmjs.org/acorn/-/acorn-2.7.0.tgz",
-      "integrity": "sha1-q259nYhqrKiwhbwzEreaGYQz8Oc=",
-      "optional": true
+      "integrity": "sha1-q259nYhqrKiwhbwzEreaGYQz8Oc="
     },
     "acorn-dynamic-import": {
       "version": "2.0.2",
@@ -2526,8 +2525,7 @@
             "ansi-regex": {
               "version": "2.1.1",
               "bundled": true,
-              "dev": true,
-              "optional": true
+              "dev": true
             },
             "aproba": {
               "version": "1.2.0",
@@ -2548,14 +2546,12 @@
             "balanced-match": {
               "version": "1.0.0",
               "bundled": true,
-              "dev": true,
-              "optional": true
+              "dev": true
             },
             "brace-expansion": {
               "version": "1.1.11",
               "bundled": true,
               "dev": true,
-              "optional": true,
               "requires": {
                 "balanced-match": "^1.0.0",
                 "concat-map": "0.0.1"
@@ -2570,20 +2566,17 @@
             "code-point-at": {
               "version": "1.1.0",
               "bundled": true,
-              "dev": true,
-              "optional": true
+              "dev": true
             },
             "concat-map": {
               "version": "0.0.1",
               "bundled": true,
-              "dev": true,
-              "optional": true
+              "dev": true
             },
             "console-control-strings": {
               "version": "1.1.0",
               "bundled": true,
-              "dev": true,
-              "optional": true
+              "dev": true
             },
             "core-util-is": {
               "version": "1.0.2",
@@ -2700,8 +2693,7 @@
             "inherits": {
               "version": "2.0.3",
               "bundled": true,
-              "dev": true,
-              "optional": true
+              "dev": true
             },
             "ini": {
               "version": "1.3.5",
@@ -2713,7 +2705,6 @@
               "version": "1.0.0",
               "bundled": true,
               "dev": true,
-              "optional": true,
               "requires": {
                 "number-is-nan": "^1.0.0"
               }
@@ -2728,7 +2719,6 @@
               "version": "3.0.4",
               "bundled": true,
               "dev": true,
-              "optional": true,
               "requires": {
                 "brace-expansion": "^1.1.7"
               }
@@ -2736,14 +2726,12 @@
             "minimist": {
               "version": "0.0.8",
               "bundled": true,
-              "dev": true,
-              "optional": true
+              "dev": true
             },
             "minipass": {
               "version": "2.2.4",
               "bundled": true,
               "dev": true,
-              "optional": true,
               "requires": {
                 "safe-buffer": "^5.1.1",
                 "yallist": "^3.0.0"
@@ -2762,7 +2750,6 @@
               "version": "0.5.1",
               "bundled": true,
               "dev": true,
-              "optional": true,
               "requires": {
                 "minimist": "0.0.8"
               }
@@ -2843,8 +2830,7 @@
             "number-is-nan": {
               "version": "1.0.1",
               "bundled": true,
-              "dev": true,
-              "optional": true
+              "dev": true
             },
             "object-assign": {
               "version": "4.1.1",
@@ -2856,7 +2842,6 @@
               "version": "1.4.0",
               "bundled": true,
               "dev": true,
-              "optional": true,
               "requires": {
                 "wrappy": "1"
               }
@@ -2942,8 +2927,7 @@
             "safe-buffer": {
               "version": "5.1.1",
               "bundled": true,
-              "dev": true,
-              "optional": true
+              "dev": true
             },
             "safer-buffer": {
               "version": "2.1.2",
@@ -2979,7 +2963,6 @@
               "version": "1.0.2",
               "bundled": true,
               "dev": true,
-              "optional": true,
               "requires": {
                 "code-point-at": "^1.0.0",
                 "is-fullwidth-code-point": "^1.0.0",
@@ -2999,7 +2982,6 @@
               "version": "3.0.1",
               "bundled": true,
               "dev": true,
-              "optional": true,
               "requires": {
                 "ansi-regex": "^2.0.0"
               }
@@ -3043,14 +3025,12 @@
             "wrappy": {
               "version": "1.0.2",
               "bundled": true,
-              "dev": true,
-              "optional": true
+              "dev": true
             },
             "yallist": {
               "version": "3.0.2",
               "bundled": true,
-              "dev": true,
-              "optional": true
+              "dev": true
             }
           }
         },
@@ -3758,8 +3738,7 @@
     "cssom": {
       "version": "0.3.2",
       "resolved": "https://registry.npmjs.org/cssom/-/cssom-0.3.2.tgz",
-      "integrity": "sha1-uANhcMefB6kP8vFuIihAJ6JDhIs=",
-      "optional": true
+      "integrity": "sha1-uANhcMefB6kP8vFuIihAJ6JDhIs="
     },
     "cssstyle": {
       "version": "0.2.37",
@@ -3873,6 +3852,15 @@
         }
       }
     },
+    "danger-plugin-no-test-shortcuts": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/danger-plugin-no-test-shortcuts/-/danger-plugin-no-test-shortcuts-2.0.0.tgz",
+      "integrity": "sha1-Atu3JFWBlFTTbNWVLi/w9H34ENo=",
+      "dev": true,
+      "requires": {
+        "lodash": "^4.17.4"
+      }
+    },
     "dashdash": {
       "version": "1.14.1",
       "resolved": "https://registry.npmjs.org/dashdash/-/dashdash-1.14.1.tgz",
@@ -8807,7 +8795,6 @@
           "version": "0.1.4",
           "bundled": true,
           "dev": true,
-          "optional": true,
           "requires": {
             "kind-of": "^3.0.2",
             "longest": "^1.0.1",
@@ -9838,8 +9825,7 @@
         "longest": {
           "version": "1.0.1",
           "bundled": true,
-          "dev": true,
-          "optional": true
+          "dev": true
         },
         "loose-envify": {
           "version": "1.3.1",
diff --git a/package.json b/package.json
index 5384375e93..67950e268c 100644
--- a/package.json
+++ b/package.json
@@ -120,6 +120,7 @@
     "classnames": "^2.2.5",
     "concurrently": "^3.5.1",
     "danger": "^3.7.13",
+    "danger-plugin-no-test-shortcuts": "^2.0.0",
     "dejavu-fonts-ttf": "^2.37.3",
     "eslint": "^5.0.1",
     "eslint-config-prettier": "^3.0.1",
diff --git a/services/npm/npm.tester.js b/services/npm/npm.tester.js
index 0da4da90f6..3f1cd59f78 100644
--- a/services/npm/npm.tester.js
+++ b/services/npm/npm.tester.js
@@ -213,7 +213,6 @@ t.create('license when network is off')
 // This tests error-handling functionality in NpmBase.
 t.create('when json is malformed for scoped package')
   .get('/l/@cycle%2Fcore.json')
-  .only()
   .intercept(nock =>
     nock('https://registry.npmjs.org')
       .get('/@cycle%2Fcore')