diff --git a/spec/filesystem-manager-spec.js b/spec/filesystem-manager-spec.js
new file mode 100644
index 000000000..dbc79fa52
--- /dev/null
+++ b/spec/filesystem-manager-spec.js
@@ -0,0 +1,137 @@
+/** @babel */
+
+import {it, beforeEach, afterEach, promisifySome} from './async-spec-helpers'
+import tempCb from 'temp'
+import fsCb from 'fs-plus'
+import path from 'path'
+
+import {CompositeDisposable} from 'event-kit'
+import FileSystemManager from '../src/filesystem-manager'
+
+tempCb.track()
+
+const fs = promisifySome(fsCb, ['writeFile', 'mkdir', 'symlink', 'appendFile', 'realpath'])
+const temp = promisifySome(tempCb, ['mkdir', 'cleanup'])
+
+describe('FileSystemManager', function () {
+  let subs, manager
+
+  beforeEach(function () {
+    subs = new CompositeDisposable()
+    manager = new FileSystemManager()
+  })
+
+  afterEach(async function () {
+    subs.dispose()
+
+    const cleanup = [temp.cleanup()]
+    const nativeWatchers = manager.nativeWatchers.tree.leaves().map(node => node.getNativeWatcher())
+    for (const native of nativeWatchers) {
+      cleanup.push(native.stop())
+    }
+    await Promise.all(cleanup)
+  })
+
+  function waitForEvent (fn) {
+    return new Promise(resolve => {
+      subs.add(fn(resolve))
+    })
+  }
+
+  function waitForChanges (watcher, ...fileNames) {
+    const waiting = new Set(fileNames)
+    const relevantEvents = []
+
+    return new Promise(resolve => {
+      const sub = watcher.onDidChange(events => {
+        for (const event of events) {
+          if (waiting.delete(event.oldPath)) {
+            relevantEvents.push(event)
+          }
+        }
+
+        if (waiting.size === 0) {
+          resolve(relevantEvents)
+          sub.dispose()
+        }
+      })
+    })
+  }
+
+  describe('getWatcher()', function () {
+    it('broadcasts onDidStart when the watcher begins listening', async function () {
+      const rootDir = await temp.mkdir('atom-fsmanager-')
+
+      const watcher = manager.getWatcher(rootDir)
+      await waitForEvent(cb => watcher.onDidStart(cb))
+    })
+
+    it('reuses an existing native watcher and broadcasts onDidStart immediately if attached to an existing watcher', async function () {
+      const rootDir = await temp.mkdir('atom-fsmanager-')
+
+      const watcher0 = manager.getWatcher(rootDir)
+      await waitForEvent(cb => watcher0.onDidStart(cb))
+
+      const watcher1 = manager.getWatcher(rootDir)
+      await waitForEvent(cb => watcher1.onDidStart(cb))
+
+      expect(watcher0.native).toBe(watcher1.native)
+    })
+
+    it('reuses an existing native watcher on a parent directory and filters events', async function () {
+      const rootDir = await temp.mkdir('atom-fsmanager-').then(fs.realpath)
+
+      const rootFile = path.join(rootDir, 'rootfile.txt')
+      const subDir = path.join(rootDir, 'subdir')
+      const subFile = path.join(subDir, 'subfile.txt')
+      await Promise.all([
+        fs.mkdir(subDir).then(
+          fs.writeFile(subFile, 'subfile\n', {encoding: 'utf8'})
+        ),
+        fs.writeFile(rootFile, 'rootfile\n', {encoding: 'utf8'})
+      ])
+
+      const rootWatcher = manager.getWatcher(rootDir)
+      await waitForEvent(cb => rootWatcher.onDidStart(cb))
+
+      const childWatcher = manager.getWatcher(subDir)
+      await waitForEvent(cb => childWatcher.onDidStart(cb))
+
+      expect(rootWatcher.native).toBe(childWatcher.native)
+
+      const firstRootChange = waitForChanges(rootWatcher, subFile)
+      const firstChildChange = waitForChanges(childWatcher, subFile)
+
+      console.log(`changing ${subFile}`)
+      await fs.appendFile(subFile, 'changes\n', {encoding: 'utf8'})
+      const firstPayloads = await Promise.all([firstRootChange, firstChildChange])
+
+      for (const events of firstPayloads) {
+        expect(events.length).toBe(1)
+        expect(events[0].oldPath).toBe(subFile)
+      }
+
+      const nextRootEvent = waitForChanges(rootWatcher, rootFile)
+      await fs.appendFile(rootFile, 'changes\n', {encoding: 'utf8'})
+
+      const nextPayload = await nextRootEvent
+
+      expect(nextPayload.length).toBe(1)
+      expect(nextPayload[0].oldPath).toBe(rootFile)
+    })
+
+    xit('adopts existing child watchers and filters events appropriately to them')
+
+    describe('event normalization', function () {
+      xit('normalizes "changed" events')
+      xit('normalizes "added" events')
+      xit('normalizes "deleted" events')
+      xit('normalizes "renamed" events')
+    })
+
+    describe('symlinks', function () {
+      xit('reports events with symlink paths')
+      xit('uses the same native watcher even for symlink paths')
+    })
+  })
+})