diff --git a/.travis.yml b/.travis.yml
index d26fa029c..b0141d322 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,7 +10,8 @@ node_js:
  - node # safety net; don't remove
 
 script:
-- make test-travisci
+  - make test-travisci
+  - codecov
 
 env:
   global:
diff --git a/README.md b/README.md
index 5d4bfa702..28f86cdc1 100644
--- a/README.md
+++ b/README.md
@@ -49,10 +49,10 @@
       src="https://img.shields.io/travis/chaijs/chai/master.svg?style=flat-square"
     />
   </a>
-  <a href="https://coveralls.io/r/chaijs/chai">
+  <a href="https://codecov.io/gh/chaijs/chai">
     <img
       alt="coverage:?"
-      src="https://img.shields.io/coveralls/chaijs/chai/master.svg?style=flat-square"
+      src="https://img.shields.io/codecov/c/github/chaijs/chai.svg?style=flat-square"
     />
   </a>
   <a href="">
diff --git a/package-lock.json b/package-lock.json
index 54b76a4be..a202fb78d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "chai",
-  "version": "4.1.1",
+  "version": "4.1.2",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -56,6 +56,27 @@
         }
       }
     },
+    "ajv": {
+      "version": "4.11.8",
+      "resolved": "https://registry.npmjs.org/ajv/-/ajv-4.11.8.tgz",
+      "integrity": "sha1-gv+wKynmYq5TvcIK8VlHcGc5xTY=",
+      "dev": true,
+      "requires": {
+        "co": "4.6.0",
+        "json-stable-stringify": "1.0.1"
+      },
+      "dependencies": {
+        "json-stable-stringify": {
+          "version": "1.0.1",
+          "resolved": "https://registry.npmjs.org/json-stable-stringify/-/json-stable-stringify-1.0.1.tgz",
+          "integrity": "sha1-mnWdOcXy/1A/1TAGRu1EX4jE+a8=",
+          "dev": true,
+          "requires": {
+            "jsonify": "0.0.0"
+          }
+        }
+      }
+    },
     "align-text": {
       "version": "0.1.4",
       "resolved": "https://registry.npmjs.org/align-text/-/align-text-0.1.4.tgz",
@@ -88,7 +109,7 @@
     "anymatch": {
       "version": "1.3.2",
       "resolved": "https://registry.npmjs.org/anymatch/-/anymatch-1.3.2.tgz",
-      "integrity": "sha512-0XNayC8lTHQ2OI8aljNCN3sSx6hsr/1+rlcDAotXJR7C1oZZHCNsfpbKwMjRA3Uqb5tF1Rae2oloTr4xpq+WjA==",
+      "integrity": "sha1-VT3Lj5HjyImEXf26NMd3IbkLnXo=",
       "dev": true,
       "requires": {
         "micromatch": "2.3.11",
@@ -115,7 +136,7 @@
         "async": {
           "version": "2.5.0",
           "resolved": "https://registry.npmjs.org/async/-/async-2.5.0.tgz",
-          "integrity": "sha512-e+lJAJeNWuPCNyxZKOBdaJGyLGHugXVQtrAwtuAe2vhxTYxFTKE73p8JuTmdH0qdQZtDvI4dhJwjZc5zsfIsYw==",
+          "integrity": "sha1-hDGQ/WtzV6C54clW7d3V7IRitU0=",
           "dev": true,
           "requires": {
             "lodash": "4.17.4"
@@ -160,6 +181,12 @@
         "sprintf-js": "1.0.3"
       }
     },
+    "argv": {
+      "version": "0.0.2",
+      "resolved": "https://registry.npmjs.org/argv/-/argv-0.0.2.tgz",
+      "integrity": "sha1-7L0W+JSbFXGDcRsb2jNPN4QBhas=",
+      "dev": true
+    },
     "arr-diff": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/arr-diff/-/arr-diff-2.0.0.tgz",
@@ -172,7 +199,7 @@
     "arr-flatten": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/arr-flatten/-/arr-flatten-1.1.0.tgz",
-      "integrity": "sha512-L3hKV5R/p5o81R7O02IGnwpDmkp6E982XhtbuwSe3O4qOtMMMtodicASA1Cny2U+aCXcNpml+m4dPsvsJ3jatg==",
+      "integrity": "sha1-NgSLv/TntH4TZkQxbJlmnqWukfE=",
       "dev": true
     },
     "array-filter": {
@@ -308,7 +335,7 @@
     "base64-js": {
       "version": "1.2.1",
       "resolved": "https://registry.npmjs.org/base64-js/-/base64-js-1.2.1.tgz",
-      "integrity": "sha512-dwVUVIXsBZXwTuwnXI9RK8sBmgq09NDHzyR9SAph9eqk76gKK2JSQmZARC2zRC81JC2QTtxD0ARU5qTS25gIGw==",
+      "integrity": "sha1-qRlH2h9KUW6jjltOwOw3c2deCIY=",
       "dev": true
     },
     "base64id": {
@@ -708,7 +735,7 @@
     "cipher-base": {
       "version": "1.0.4",
       "resolved": "https://registry.npmjs.org/cipher-base/-/cipher-base-1.0.4.tgz",
-      "integrity": "sha512-Kkht5ye6ZGmwv40uUDZztayT2ThLQGfnj/T71N/XzeZeo3nf8foyW7zGTsPYkEya3m5f3cAypH+qe7YOrM1U2Q==",
+      "integrity": "sha1-h2Dk7MJy9MNjUy+SbYdKriwTl94=",
       "dev": true,
       "requires": {
         "inherits": "2.0.3",
@@ -736,6 +763,80 @@
         }
       }
     },
+    "co": {
+      "version": "4.6.0",
+      "resolved": "https://registry.npmjs.org/co/-/co-4.6.0.tgz",
+      "integrity": "sha1-bqa989hTrlTMuOR7+gvz+QMfsYQ=",
+      "dev": true
+    },
+    "codecov": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/codecov/-/codecov-3.0.0.tgz",
+      "integrity": "sha1-wnO4xPEpRXI+jcnSWAPYk0Pl8o4=",
+      "dev": true,
+      "requires": {
+        "argv": "0.0.2",
+        "request": "2.81.0",
+        "urlgrey": "0.4.4"
+      },
+      "dependencies": {
+        "caseless": {
+          "version": "0.12.0",
+          "resolved": "https://registry.npmjs.org/caseless/-/caseless-0.12.0.tgz",
+          "integrity": "sha1-G2gcIf+EAzyCZUMJBolCDRhxUdw=",
+          "dev": true
+        },
+        "har-validator": {
+          "version": "4.2.1",
+          "resolved": "https://registry.npmjs.org/har-validator/-/har-validator-4.2.1.tgz",
+          "integrity": "sha1-M0gdDxu/9gDdID11gSpqX7oALio=",
+          "dev": true,
+          "requires": {
+            "ajv": "4.11.8",
+            "har-schema": "1.0.5"
+          }
+        },
+        "request": {
+          "version": "2.81.0",
+          "resolved": "https://registry.npmjs.org/request/-/request-2.81.0.tgz",
+          "integrity": "sha1-xpKJRqDgbF+Nb4qTM0af/aRimKA=",
+          "dev": true,
+          "requires": {
+            "aws-sign2": "0.6.0",
+            "aws4": "1.6.0",
+            "caseless": "0.12.0",
+            "combined-stream": "1.0.5",
+            "extend": "3.0.1",
+            "forever-agent": "0.6.1",
+            "form-data": "2.1.4",
+            "har-validator": "4.2.1",
+            "hawk": "3.1.3",
+            "http-signature": "1.1.1",
+            "is-typedarray": "1.0.0",
+            "isstream": "0.1.2",
+            "json-stringify-safe": "5.0.1",
+            "mime-types": "2.1.16",
+            "oauth-sign": "0.8.2",
+            "performance-now": "0.2.0",
+            "qs": "6.4.0",
+            "safe-buffer": "5.1.1",
+            "stringstream": "0.0.5",
+            "tough-cookie": "2.3.2",
+            "tunnel-agent": "0.6.0",
+            "uuid": "3.1.0"
+          }
+        },
+        "tunnel-agent": {
+          "version": "0.6.0",
+          "resolved": "https://registry.npmjs.org/tunnel-agent/-/tunnel-agent-0.6.0.tgz",
+          "integrity": "sha1-J6XeoGs2sEoKmWZ3SykIaPD8QP0=",
+          "dev": true,
+          "requires": {
+            "safe-buffer": "5.1.1"
+          }
+        }
+      }
+    },
     "colors": {
       "version": "1.1.2",
       "resolved": "https://registry.npmjs.org/colors/-/colors-1.1.2.tgz",
@@ -783,7 +884,7 @@
     "commander": {
       "version": "2.11.0",
       "resolved": "https://registry.npmjs.org/commander/-/commander-2.11.0.tgz",
-      "integrity": "sha512-b0553uYA5YAEGgyYIGYROzKQ7X5RAqedkfjiZxwi0kL1g3bOaBNNZfYkzt/CL0umgD5wc9Jec2FbB98CjkMRvQ==",
+      "integrity": "sha1-FXFS/R56bI2YpbcVzzdt+SgARWM=",
       "dev": true
     },
     "component-bind": {
@@ -976,7 +1077,7 @@
     "crypto-browserify": {
       "version": "3.11.1",
       "resolved": "https://registry.npmjs.org/crypto-browserify/-/crypto-browserify-3.11.1.tgz",
-      "integrity": "sha512-Na7ZlwCOqoaW5RwUK1WpXws2kv8mNhWdTlzob0UXulk6G9BDbyiJaGTYBIX61Ozn9l1EPPJpICZb4DaOpT9NlQ==",
+      "integrity": "sha1-lIlF78Z1ekANbl5a9HGU0QBkJ58=",
       "dev": true,
       "requires": {
         "browserify-cipher": "1.0.0",
@@ -1665,7 +1766,7 @@
     "glob": {
       "version": "7.1.2",
       "resolved": "https://registry.npmjs.org/glob/-/glob-7.1.2.tgz",
-      "integrity": "sha512-MJTUg1kjuLeQCJ+ccE4Vpa6kKVXkPYJ2mOCQyUuKLcLQsdrMCpBPUi8qVE6+YuaJkozeA9NusTAw3hLr8Xe5EQ==",
+      "integrity": "sha1-wZyd+aAocC1nhhI4SmVSQExjbRU=",
       "dev": true,
       "requires": {
         "fs.realpath": "1.0.0",
@@ -1736,6 +1837,12 @@
         }
       }
     },
+    "har-schema": {
+      "version": "1.0.5",
+      "resolved": "https://registry.npmjs.org/har-schema/-/har-schema-1.0.5.tgz",
+      "integrity": "sha1-0mMTX0MwfALGAq/I/pWXDAFRNp4=",
+      "dev": true
+    },
     "har-validator": {
       "version": "2.0.6",
       "resolved": "https://registry.npmjs.org/har-validator/-/har-validator-2.0.6.tgz",
@@ -1807,7 +1914,7 @@
     "hash.js": {
       "version": "1.1.3",
       "resolved": "https://registry.npmjs.org/hash.js/-/hash.js-1.1.3.tgz",
-      "integrity": "sha512-/UETyP0W22QILqS+6HowevwhEFJ3MBJnwTf75Qob9Wz9t0DPuisL8kW8YZMK62dHAKE1c1p+gY1TtOLY+USEHA==",
+      "integrity": "sha1-NA3tvmKQGHFRweodd3o0SJNd+EY=",
       "dev": true,
       "requires": {
         "inherits": "2.0.3",
@@ -2167,7 +2274,7 @@
         "esprima": {
           "version": "4.0.0",
           "resolved": "https://registry.npmjs.org/esprima/-/esprima-4.0.0.tgz",
-          "integrity": "sha512-oftTcaMu/EGrEIu904mWteKIv8vMuOgGYo7EhVJJN00R/EED9DCua/xxHRdYnKtcECzVg7xOWhflvJMnqcFZjw==",
+          "integrity": "sha1-RJnt3NERDgshi6zy+n9/WfVcqAQ=",
           "dev": true
         }
       }
@@ -2628,7 +2735,7 @@
     "minimatch": {
       "version": "3.0.4",
       "resolved": "https://registry.npmjs.org/minimatch/-/minimatch-3.0.4.tgz",
-      "integrity": "sha512-yJHVQEhyqPLUTgt9B83PXu6W3rx4MvvHvSUvToogpwoGDOUQ+yDrR0HRot+yOCdCO7u4hX3pWft6kWBBcqh0UA==",
+      "integrity": "sha1-UWbihkV/AzBgZL5Ul+jbsMPTIIM=",
       "dev": true,
       "requires": {
         "brace-expansion": "1.1.8"
@@ -3001,6 +3108,12 @@
       "integrity": "sha1-elfrVQpng/kRUzH89GY9XI4AelA=",
       "dev": true
     },
+    "performance-now": {
+      "version": "0.2.0",
+      "resolved": "https://registry.npmjs.org/performance-now/-/performance-now-0.2.0.tgz",
+      "integrity": "sha1-M+8wxcd9TqIcWlOGnZG1bY8lVeU=",
+      "dev": true
+    },
     "phantomjs-prebuilt": {
       "version": "2.1.14",
       "resolved": "https://registry.npmjs.org/phantomjs-prebuilt/-/phantomjs-prebuilt-2.1.14.tgz",
@@ -3115,7 +3228,7 @@
     "randomatic": {
       "version": "1.1.7",
       "resolved": "https://registry.npmjs.org/randomatic/-/randomatic-1.1.7.tgz",
-      "integrity": "sha512-D5JUjPyJbaJDkuAazpVnSfVkLlpeO3wDlPROTMLGKG1zMFNFRgrciKo1ltz/AzNTkqE0HzDx655QOL51N06how==",
+      "integrity": "sha1-x6vpzIuHwLqodrGf3oP9RkeX44w=",
       "dev": true,
       "requires": {
         "is-number": "3.0.0",
@@ -3156,7 +3269,7 @@
     "randombytes": {
       "version": "2.0.5",
       "resolved": "https://registry.npmjs.org/randombytes/-/randombytes-2.0.5.tgz",
-      "integrity": "sha512-8T7Zn1AhMsQ/HI1SjcCfT/t4ii3eAqco3yOcSzS4mozsOz69lHLsoMXmF9nZgnFanYscnSlUSgs8uZyKzpE6kg==",
+      "integrity": "sha1-3ACaJGuNCaF3tLegrne8Vw9LG3k=",
       "dev": true,
       "requires": {
         "safe-buffer": "5.1.1"
@@ -3191,7 +3304,7 @@
     "readable-stream": {
       "version": "2.3.3",
       "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-2.3.3.tgz",
-      "integrity": "sha512-m+qzzcn7KUxEmd1gMbchF+Y2eIUbieUaxkWtptyHywrX0rE8QEYqPC07Vuy4Wm32/xE16NcdBctb8S0Xe/5IeQ==",
+      "integrity": "sha1-No8lEtefnUb9/HE0mueHi7weuVw=",
       "dev": true,
       "requires": {
         "core-util-is": "1.0.2",
@@ -3335,7 +3448,7 @@
     "safe-buffer": {
       "version": "5.1.1",
       "resolved": "https://registry.npmjs.org/safe-buffer/-/safe-buffer-5.1.1.tgz",
-      "integrity": "sha512-kKvNJn6Mm93gAczWVJg7wH+wGYWNrDHdWvpUmHyEsgCtIwwo3bqPtV4tR5tuPaUhTOo/kvhVwd8XwwOllGYkbg==",
+      "integrity": "sha1-iTMSr2myEj3vcfV4iQAWce6yyFM=",
       "dev": true
     },
     "sauce-connect-launcher": {
@@ -3649,7 +3762,7 @@
     "stream-http": {
       "version": "2.7.2",
       "resolved": "https://registry.npmjs.org/stream-http/-/stream-http-2.7.2.tgz",
-      "integrity": "sha512-c0yTD2rbQzXtSsFSVhtpvY/vS6u066PcXOX9kBB3mSO76RiUQzL340uJkGBWnlBg4/HZzqiUXtaVA7wcRcJgEw==",
+      "integrity": "sha1-QKBQ7I3DtTsz2ZCUFcAsC/Gr+60=",
       "dev": true,
       "requires": {
         "builtin-status-codes": "3.0.0",
@@ -3672,7 +3785,7 @@
     "string_decoder": {
       "version": "1.0.3",
       "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.0.3.tgz",
-      "integrity": "sha512-4AH6Z5fzNNBcH+6XDMfA/BTt87skxqJlO0lAh3Dker5zThcAxG6mKz+iGu308UKoPPQ8Dcqx/4JhujzltRa+hQ==",
+      "integrity": "sha1-D8Z9fBQYJd6UKC3VNr7GubzoYKs=",
       "dev": true,
       "requires": {
         "safe-buffer": "5.1.1"
@@ -3907,6 +4020,12 @@
         }
       }
     },
+    "urlgrey": {
+      "version": "0.4.4",
+      "resolved": "https://registry.npmjs.org/urlgrey/-/urlgrey-0.4.4.tgz",
+      "integrity": "sha1-iS/pWWCAXoVRnxzUOJ8stMu3ZS8=",
+      "dev": true
+    },
     "useragent": {
       "version": "2.2.1",
       "resolved": "https://registry.npmjs.org/useragent/-/useragent-2.2.1.tgz",
@@ -3949,7 +4068,7 @@
     "uuid": {
       "version": "3.1.0",
       "resolved": "https://registry.npmjs.org/uuid/-/uuid-3.1.0.tgz",
-      "integrity": "sha512-DIWtzUkw04M4k3bf1IcpS2tngXEL26YUD2M0tMDUpnUrz2hgzUBlD55a4FjdLGPvfHxS6uluGWvaVEqgBcVa+g==",
+      "integrity": "sha1-PdPT55Crwk17DToDT/q6vijrvAQ=",
       "dev": true
     },
     "vargs": {
diff --git a/package.json b/package.json
index 41122e3b3..ee94bd43f 100644
--- a/package.json
+++ b/package.json
@@ -43,6 +43,7 @@
   "devDependencies": {
     "browserify": "^14.4.0",
     "bump-cli": "^1.1.3",
+    "codecov": "^3.0.0",
     "istanbul": "^0.4.3",
     "karma": "^1.0.0",
     "karma-firefox-launcher": "^1.0.0",