diff --git a/Cakefile b/Cakefile
index 01fdd1e2e8..a43239a5f7 100644
--- a/Cakefile
+++ b/Cakefile
@@ -376,7 +376,6 @@ task 'bench', 'quick benchmark of compilation time', ->
 # Run the CoffeeScript test suite.
 runTests = (CoffeeScript) ->
   CoffeeScript.register() unless global.testingBrowser
-  startTime = Date.now()
 
   # These are attached to `global` so that they’re accessible from within
   # `test/async.coffee`, which has an async-capable version of
@@ -396,29 +395,35 @@ runTests = (CoffeeScript) ->
   global.yellow = yellow
   global.reset  = reset
 
+  asyncTests = []
+  onFail = (description, fn, err) ->
+    failures.push
+      filename: global.currentFile
+      error: err
+      description: description
+      source: fn.toString() if fn.toString?
+
   # Our test helper function for delimiting different test cases.
   global.test = (description, fn) ->
     try
       fn.test = {description, currentFile}
-      fn.call(fn)
-      ++passedTests
-    catch e
-      failures.push
-        filename: currentFile
-        error: e
-        description: description if description?
-        source: fn.toString() if fn.toString?
-
-  global.supportsAsync = if global.testingBrowser
-    try
+      result = fn.call(fn)
+      if result instanceof Promise # An async test.
+        asyncTests.push result
+        result.then ->
+          passedTests++
+        .catch (err) ->
+          onFail description, fn, err
+      else
+        passedTests++
+    catch err
+      onFail description, fn, err
+
+  global.supportsAsync = try
       new Function('async () => {}')()
       yes
     catch
       no
-  else
-    [major, minor, build] = process.versions.node.split('.').map (version) ->
-      parseInt version, 10
-    major >= 8 or (major is 7 and minor >= 6)
 
   helpers.extend global, require './test/support/helpers'
 
@@ -442,6 +447,7 @@ runTests = (CoffeeScript) ->
   unless global.supportsAsync # Except for async tests, if async isn’t supported.
     files = files.filter (filename) -> filename isnt 'async.coffee'
 
+  startTime = Date.now()
   for file in files when helpers.isCoffee file
     literate = helpers.isLiterate file
     currentFile = filename = path.join 'test', file
@@ -450,12 +456,13 @@ runTests = (CoffeeScript) ->
       CoffeeScript.run code.toString(), {filename, literate}
     catch error
       failures.push {filename, error}
-  return !failures.length
+
+  Promise.all(asyncTests).then ->
+    Promise.reject() if failures.length isnt 0
 
 
 task 'test', 'run the CoffeeScript language test suite', ->
-  testResults = runTests CoffeeScript
-  process.exit 1 unless testResults
+  runTests(CoffeeScript).catch -> process.exit 1
 
 
 task 'test:browser', 'run the test suite against the merged browser script', ->
@@ -463,8 +470,8 @@ task 'test:browser', 'run the test suite against the merged browser script', ->
   result = {}
   global.testingBrowser = yes
   (-> eval source).call result
-  testResults = runTests result.CoffeeScript
-  process.exit 1 unless testResults
+  runTests(CoffeeScript).catch -> process.exit 1
+
 
 task 'test:integrations', 'test the module integrated with other libraries and environments', ->
   # Tools like Webpack and Browserify generate builds intended for a browser
diff --git a/documentation/test.html b/documentation/test.html
index 3254e97574..dc2ad5abef 100644
--- a/documentation/test.html
+++ b/documentation/test.html
@@ -52,16 +52,27 @@ <h1>CoffeeScript Test Suite</h1>
   stdout.appendChild div
   msg
 
+asyncTests = []
+onFail = (description, fn, err) ->
+  failures.push
+    error: err
+    description: description
+    source: fn.toString() if fn.toString?
+
 @test = (description, fn) ->
   ++total
   try
-    fn.call(fn)
-    ++passedTests
-  catch error
-    failures.push
-      error: error
-      description: description
-      source: fn.toString() if fn.toString?
+    result = fn.call(fn)
+    if result instanceof Promise # An async test.
+      asyncTests.push result
+      result.then ->
+        passedTests++
+      .catch (err) ->
+        onFail description, fn, err
+    else
+      passedTests++
+  catch err
+    onFail description, fn, err
 
 @failures =
   push: (failure) -> # Match function called by regular tests
@@ -74,11 +85,11 @@ <h1>CoffeeScript Test Suite</h1>
 @ok = (good, msg = 'Error') ->
   throw Error msg unless good
 
-# Polyfill Node assert's fail
+# Polyfill Node assert’s fail
 @fail = ->
   ok no
 
-# Polyfill Node assert's deepEqual with Underscore's isEqual
+# Polyfill Node assert’s deepEqual with Underscore’s isEqual
 @deepEqual = (a, b) ->
   ok _.isEqual(a, b), "Expected #{JSON.stringify a} to deep equal #{JSON.stringify b}"
 
@@ -114,11 +125,14 @@ <h1>CoffeeScript Test Suite</h1>
   CoffeeScript.run test.innerHTML, options
 
 # Finish up
-yay = passedTests is total and not failedTests
-sec = (new Date - start) / 1000
-msg = "passed #{passedTests} tests in #{sec.toFixed 2} seconds"
-msg = "failed #{total - passedTests} tests and #{msg}" unless yay
-say msg, (if yay then 'good' else 'bad')
+done = ->
+  yay = passedTests is total and not failedTests
+  sec = (new Date - start) / 1000
+  msg = "passed #{passedTests} tests in #{sec.toFixed 2} seconds"
+  msg = "failed #{total - passedTests} tests and #{msg}" unless yay
+  say msg, (if yay then 'good' else 'bad')
+
+Promise.all(asyncTests).then(done).catch(done)
 </script>
 
 <%= tests %>
diff --git a/test/async.coffee b/test/async.coffee
index cb71d2f1bd..be1994c589 100644
--- a/test/async.coffee
+++ b/test/async.coffee
@@ -1,28 +1,15 @@
-# Functions that contain the `await` keyword will compile into async
-# functions, which currently only Node 7+ in harmony mode can even
-# evaluate, much less run. Therefore we need to prevent runtimes
-# which will choke on such code from even loading it. This file is
-# only loaded by async-capable environments, so we redefine `test`
-# here even though it is based on `test` defined in `Cakefile`.
-# It replaces `test` for this file, and adds to the tracked
-# `passedTests` and `failures` arrays which are global objects.
-test = (description, fn) ->
-  try
-    fn.test = {description, currentFile}
-    await fn.call(fn)
-    ++passedTests
-  catch e
-    failures.push
-      filename: currentFile
-      error: e
-      description: description if description?
-      source: fn.toString() if fn.toString?
-
-
-# always fulfills
+# Functions that contain the `await` keyword will compile into async functions,
+# supported by Node 7.6+, Chrome 55+, Firefox 52+, Safari 10.1+ and Edge.
+# But runtimes that don’t support the `await` keyword will throw an error,
+# even if we put `return unless global.supportsAsync` at the top of this file.
+# Therefore we need to prevent runtimes which will choke on such code from even
+# parsing it, which is handled in `Cakefile`.
+
+
+# This is always fulfilled.
 winning = (val) -> Promise.resolve val
 
-# always is rejected
+# This is always rejected.
 failing = (val) -> Promise.reject new Error val
 
 
diff --git a/test/error_messages.coffee b/test/error_messages.coffee
index 640e46c432..ca583e888a 100644
--- a/test/error_messages.coffee
+++ b/test/error_messages.coffee
@@ -91,6 +91,9 @@ if require?
     notEqual error.stack.toString().indexOf(filePath), -1
 
   test "#4418: stack traces for compiled files reference the correct line number", ->
+    # The browser is already compiling other anonymous scripts (the tests)
+    # which will conflict.
+    return if global.testingBrowser
     filePath = path.join os.tmpdir(), 'StackTraceLineNumberTestFile.coffee'
     fileContents = """
       testCompiledFileStackTraceLineNumber = ->
@@ -112,6 +115,9 @@ if require?
 
 
 test "#4418: stack traces for compiled strings reference the correct line number", ->
+  # The browser is already compiling other anonymous scripts (the tests)
+  # which will conflict.
+  return if global.testingBrowser
   try
     CoffeeScript.run '''
       testCompiledStringStackTraceLineNumber = ->
@@ -128,6 +134,9 @@ test "#4418: stack traces for compiled strings reference the correct line number
 
 
 test "#4558: compiling a string inside a script doesn’t screw up stack trace line number", ->
+  # The browser is already compiling other anonymous scripts (the tests)
+  # which will conflict.
+  return if global.testingBrowser
   try
     CoffeeScript.run '''
       testCompilingInsideAScriptDoesntScrewUpStackTraceLineNumber = ->