diff --git a/changelog.md b/changelog.md
index 92aa60bd1..971a588ba 100644
--- a/changelog.md
+++ b/changelog.md
@@ -2,12 +2,18 @@
 
 //  Add your own contribution below
 
+### 0.6.0
+
+* omits flow requirement for new test files
+* adds support for circleci
+* defines CISource properties in flow as read-only
+
 ### 0.5.0
 
 * `danger.pr` -> `danger.github.pr`, I've also created interfaces for them - orta
 * `warn`, `message`, `markdown` are all ported over to DangerJS - orta
 * Shows a HTML table for Danger message - orta
-* Now offers a Flow-typed definition file, it's not shipped to their repo yet, you can make it by `npm run export-flowtype` - orta 
+* Now offers a Flow-typed definition file, it's not shipped to their repo yet, you can make it by `npm run export-flowtype` - orta
 * Started turning this into a real project by adding tests - orta
 
 ### 0.0.5-0.0.10
@@ -22,7 +28,7 @@
 
 * Danger will post a comment on a GitHub PR with any Fails - orta
 
-### 0.0.2 
+### 0.0.2
 
 OK, first usable for others version. Only supports GitHub and Travis CI.
 
@@ -30,7 +36,7 @@ You can run by doing:
 
 ```sh
 danger
-``` 
+```
 
 Make sure you set a `DANGER_GITHUB_API_TOKEN` on your CI - [see the Ruby guide](http://danger.systems/guides/getting_started.html#setting-up-danger-to-run-on-your-ci) for that.
 
@@ -42,13 +48,13 @@ git
 fail(message: string)
 ```
 
-`pr` _probably_ won't be sticking around for the long run, but if you're using a `0.0.2` release, you should be OK with that. It's the full metadata of the PR, so [this JSON file](https://raw.githubusercontent.com/danger/danger/master/spec/fixtures/github_api/pr_response.json). 
+`pr` _probably_ won't be sticking around for the long run, but if you're using a `0.0.2` release, you should be OK with that. It's the full metadata of the PR, so [this JSON file](https://raw.githubusercontent.com/danger/danger/master/spec/fixtures/github_api/pr_response.json).
 `git` currently has:
 
 ```sh
 git.modified_file
 git.created_files
-git.deleted_files 
+git.deleted_files
 ```
 
 which are string arrays of files.
@@ -66,10 +72,10 @@ if (!hasChangelog) {
 }
 ```
 
-That should do ya. I think. This doens't support babel, and I haven't explored using other modules etc, so 
+That should do ya. I think. This doens't support babel, and I haven't explored using other modules etc, so
 
 ./
 
 ### 0.0.1
 
-Not usable for others, only stubs of classes etc.
\ No newline at end of file
+Not usable for others, only stubs of classes etc.
diff --git a/circle.yml b/circle.yml
new file mode 100644
index 000000000..3db508af2
--- /dev/null
+++ b/circle.yml
@@ -0,0 +1,12 @@
+machine:
+  node:
+    version: 6.1
+
+test:
+  override:
+    - npm run build
+    - npm run link
+    - danger
+  post:
+    - npm run flow
+    - npm run lint
diff --git a/dangerfile.js b/dangerfile.js
index e0b315dca..90f35a092 100644
--- a/dangerfile.js
+++ b/dangerfile.js
@@ -12,10 +12,12 @@ if (!hasChangelog) {
 const jsFiles = danger.git.created_files.filter(path => path.endsWith("js"))
 
 // new js files should have `@flow` at the top
-const unFlowedFiles = jsFiles.filter(filepath => {
-  const content = fs.readFileSync(filepath)
-  return !content.includes("@flow")
-})
+// but exclude tests from being flow-ey
+const unFlowedFiles = jsFiles.filter(path => !path.endsWith("test.js"))
+  .filter(filepath => {
+    const content = fs.readFileSync(filepath)
+    return !content.includes("@flow")
+  })
 
 if (unFlowedFiles.length > 0) {
   warn(`These new JS files do not have Flow enabled: ${unFlowedFiles.join(", ")}`)
diff --git a/source/ci_source/Circle.js b/source/ci_source/Circle.js
new file mode 100644
index 000000000..540b3e6f2
--- /dev/null
+++ b/source/ci_source/Circle.js
@@ -0,0 +1,53 @@
+// @flow
+"use strict"
+
+import type { Env } from "./ci_source"
+import { ensureEnvKeysExist, ensureEnvKeysAreInt } from "./ci_source_helpers"
+export default class Circle {
+  env: Env
+  constructor(env: Env) { this.env = env }
+
+  get name(): string { return "Circle CI" }
+
+  get isCI(): boolean {
+    return ensureEnvKeysExist(this.env, ["CIRCLE_BUILD_NUM"])
+  }
+
+  get isPR(): boolean {
+    if (ensureEnvKeysExist(this.env, ["CI_PULL_REQUEST"])) {
+      return true
+    }
+
+    const mustHave = ["CIRCLE_CI_API_TOKEN", "CIRCLE_PROJECT_USERNAME", "CIRCLE_PROJECT_REPONAME", "CIRCLE_BUILD_NUM"]
+    return ensureEnvKeysExist(this.env, mustHave) && ensureEnvKeysAreInt(this.env, ["CIRCLE_PR_NUMBER"])
+  }
+
+  _prParseURL(): {owner?: string, reponame?: string, id?: string} {
+    const prUrl = this.env.CI_PULL_REQUEST || ""
+    const splitSlug = prUrl.split("/")
+    if (splitSlug.length === 7) {
+      const owner = splitSlug[3]
+      const reponame = splitSlug[4]
+      const id = splitSlug[6]
+      return {owner, reponame, id}
+    }
+    return {}
+  }
+
+  get pullRequestID(): string {
+    if (this.env.CIRCLE_PR_NUMBER) {
+      return this.env.CIRCLE_PR_NUMBER
+    } else {
+      const {id} = this._prParseURL()
+      return id || ""
+    }
+  }
+
+  get repoSlug(): string {
+    const {owner, reponame} = this._prParseURL()
+    return (owner && reponame) ? `${owner}/${reponame}` : ""
+  }
+
+  get repoURL(): string { return this.env.CIRCLE_REPOSITORY_URL }
+  get supportedPlatforms(): string[] { return ["github"] }
+}
diff --git a/source/ci_source/_tests/_circle.test.js b/source/ci_source/_tests/_circle.test.js
new file mode 100644
index 000000000..4abf258f0
--- /dev/null
+++ b/source/ci_source/_tests/_circle.test.js
@@ -0,0 +1,83 @@
+import Circle from "../Circle"
+
+const correctEnv = {
+  "CIRCLE_CI_API_TOKEN": "xxx",
+  "CIRCLE_PROJECT_USERNAME": "circle_org",
+  "CIRCLE_PROJECT_REPONAME": "someproject",
+  "CIRCLE_BUILD_NUM": "1501",
+  "CIRCLE_PR_NUMBER": "800",
+  "CI_PULL_REQUEST": "https://github.com/artsy/eigen/pull/800"
+}
+
+describe(".isCI", () => {
+  test("validates when all Circle environment vars are set", () => {
+    const circle = new Circle(correctEnv)
+    expect(circle.isCI).toBeTruthy()
+  })
+
+  test("does not validate without josh", () => {
+    const circle = new Circle({})
+    expect(circle.isCI).toBeFalsy()
+  })
+})
+
+describe(".isPR", () => {
+  test("validates when all circle environment vars are set", () => {
+    const circle = new Circle(correctEnv)
+    expect(circle.isPR).toBeTruthy()
+  })
+
+  test("does not validate outside of circle", () => {
+    const circle = new Circle({})
+    expect(circle.isPR).toBeFalsy()
+  })
+
+  const envs = ["CIRCLE_CI_API_TOKEN", "CIRCLE_PROJECT_USERNAME", "CIRCLE_PROJECT_REPONAME", "CIRCLE_BUILD_NUM"]
+  envs.forEach((key: string) => {
+    var env = {
+      "CIRCLE_CI_API_TOKEN": "xxx",
+      "CIRCLE_PROJECT_USERNAME": "circle_org",
+      "CIRCLE_PROJECT_REPONAME": "someproject",
+      "CIRCLE_BUILD_NUM": "1501",
+      "CIRCLE_PR_NUMBER": "800",
+      "CI_PULL_REQUEST": "https://github.com/artsy/eigen/pull/800"
+    }
+    env[key] = null
+
+    test(`does not validate when ${key} is missing`, () => {
+      const circle = new Circle({})
+      expect(circle.isPR).toBeFalsy()
+    })
+  })
+
+  it("needs to have a PR number", () => {
+    var env = {
+      "CIRCLE_PR_NUMBER": "asdasd",
+      "CIRCLE_REPO_SLUG": "artsy/eigen"
+    }
+    const circle = new Circle(env)
+    expect(circle.isPR).toBeFalsy()
+  })
+})
+
+describe(".pullReuestID", () => {
+  it("pulls it out of the env", () => {
+    const circle = new Circle({CIRCLE_PR_NUMBER: "800"})
+    expect(circle.pullRequestID).toEqual("800")
+  })
+
+  it("can derive it from PR Url", () => {
+    var env = {
+      "CI_PULL_REQUEST": "https://github.com/artsy/eigen/pull/23"
+    }
+    const circle = new Circle(env)
+    expect(circle.pullRequestID).toEqual("23")
+  })
+})
+
+describe(".repoSlug", () => {
+  it("derives it from the PR Url", () => {
+    const circle = new Circle(correctEnv)
+    expect(circle.repoSlug).toEqual("artsy/eigen")
+  })
+})
diff --git a/source/ci_source/ci_source.js b/source/ci_source/ci_source.js
index 0c3dc6601..4c02b169d 100644
--- a/source/ci_source/ci_source.js
+++ b/source/ci_source/ci_source.js
@@ -35,6 +35,7 @@ export interface CISource {
 }
 
 import Travis from "./Travis"
+import Circle from "./Circle"
 import Fake from "./Fake"
 
 /**
@@ -46,8 +47,12 @@ import Fake from "./Fake"
 export function getCISourceForEnv(env: Env) : ?CISource {
   // Fake is what I'm using during dev for the minute
   const travis = new Travis(env)
+  const circle = new Circle(env)
+
   if (travis.isCI) {
     return travis
+  } else if (circle.isCI) {
+    return circle
   } else {
     return new Fake()
   }