diff --git a/test/get-prefix.js b/test/get-prefix.js
new file mode 100644
index 0000000..45a86d5
--- /dev/null
+++ b/test/get-prefix.js
@@ -0,0 +1,79 @@
+'use strict'
+
+const os = require('os')
+const path = require('path')
+const Tacks = require('tacks')
+const test = require('tap').test
+const testDir = require('./util/test-dir.js')(__filename)
+
+const Dir = Tacks.Dir
+const File = Tacks.File
+
+const getPrefix = require('../get-prefix.js')
+
+test('navigates out of `node_modules` without fs nav', t => {
+  return getPrefix('/foo/bar/baz/node_modules/node_modules').then(val => {
+    t.equal(val, '/foo/bar/baz', 'navigates out of node_modules')
+  })
+})
+
+test('detects if currently in an npm package using package.json', t => {
+  const fixture = new Tacks(Dir({
+    'package.json': File({name: 'foo', version: '1.2.3'})
+  }))
+  fixture.create(testDir)
+  return getPrefix(testDir).then(prefix => {
+    t.equal(prefix, testDir, 'current dir worked out')
+  })
+})
+
+test('detects if currently in an npm package using node_modules', t => {
+  const fixture = new Tacks(Dir({
+    'node_modules': Dir({})
+  }))
+  fixture.create(testDir)
+  return getPrefix(testDir).then(prefix => {
+    t.equal(prefix, testDir, 'current dir worked out')
+  })
+})
+
+test('returns the same path if no package was found in parent dirs', t => {
+  // Hopefully folks' tmpdir isn't inside an npm package ;)
+  const tmp = os.tmpdir()
+  return getPrefix(tmp).then(prefix => {
+    t.equal(prefix, tmp, 'returned the same path')
+  })
+})
+
+test('navigates up the filesystem until it finds a package', t => {
+  const fixture = new Tacks(Dir({
+    'node_modules': Dir({}),
+    'a': Dir({'b': Dir({'c': Dir({'d': Dir({})})})})
+  }))
+  fixture.create(testDir)
+  return getPrefix(path.join(testDir, 'a', 'b', 'c')).then(prefix => {
+    t.equal(prefix, testDir, 'navigated all the way up')
+  })
+})
+
+test('doesn\'t go too far while navigating up', t => {
+  const fixture = new Tacks(Dir({
+    'node_modules': Dir({}),
+    'a': Dir({'node_modules': Dir({}), 'b': Dir({'c': Dir({'d': Dir({})})})})
+  }))
+  fixture.create(testDir)
+  return getPrefix(path.join(testDir, 'a', 'b', 'c')).then(prefix => {
+    t.equal(prefix, path.join(testDir, 'a'), 'stopped before root')
+  })
+})
+
+test('returns root if we get there', t => {
+  let root = '/'
+  if (process.platform === 'win32') {
+    const currentDrive = process.cwd().match(/^([a-z]+):/i)[1]
+    root = `${currentDrive}:\\`
+  }
+  return getPrefix(root).then(prefix => {
+    t.equal(prefix, root, 'used the same root')
+  })
+})