rhyskeepence / clairvoyance   1.0.142


A Scala Specs2 extension, producing human readable documentation à la Yatspec.

Scala versions: 2.13 2.12 2.11 2.10


Clairvoyance is an extension to Specs2, a Scala test library. Clairvoyance provides a few extensions to capture what is happening in your tests, and then produce business and tester friendly documentation.

It's a pastiche of Yatspec, a Java testing library written by my colleague Dan Bodart. It addresses the deficiencies we experienced with Fit and Concordion.

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class LoggingExample extends ClairvoyantSpec {
  "The coordinator" should {
    "invoke the Doomsday Device on the 21st of December 2012" in new context {
      theDoomsdayDevice should beUnleashed

  trait context extends ClairvoyantContext {
    // test set up and fixtures

It breaks down like this:

  • Create a Spec which extends ClairvoyantSpec
  • Write the spec in the mutable spec style (for various historical reasons)
  • Create a context which extends ClairvoyantContext
  • InterestingGivens can be added with statements such as interestingGivens += ("Current date" -> "21/12/2012")
  • The Scala code within the spec method is interpreted into a text specification, to encourage readability.

The full source to this example is here.

Here is the output of this spec. Example output

Get This Party Started

Add this to your SBT build:

// for Scala 2.10 and above:
libraryDependencies += "com.github.rhyskeepence" %% "clairvoyance-specs2" % <latest-version>

// for scala 2.9.x:
libraryDependencies += "com.github.rhyskeepence" %% "clairvoyance" % "27"

resolvers += "releases" at "http://oss.sonatype.org/content/repositories/releases"

Or in Maven:

    <name>sonatype releases</name>

Interesting Givens

These are inputs into your test, which may not be specified in the spec, but should be logged to the output:

  interestingGivens += ("Current date" -> "21/12/2012")


  ("Current date" -> "21/12/2012").isInteresting

Captured Inputs And Outputs

These are the inputs or outputs to your system, which may not be practical to assert upon, but should be logged.

Perhaps you are using a stub rather than communicating with a third party in your spec:

class StubGizmometer extends Gizmometer {

To capture inputs and outputs, just add the ProducesCapturedInputsAndOutputs trait and call captureValue:

class StubGizmometer extends Gizmometer with ProducesCapturedInputsAndOutputs {
  def scan(brain: Brain) {
    captureValue("Brain" -> brain)

and in your context, register the stub so that clairvoyant knows about it:

trait context extends ClairvoyantContext {
    val gizmometer = new StubGizmometer
    override def capturedInputsAndOutputs = Seq(gizmometer)

The value that is captured can be of any type. XML is formatted nicely, and HTML can be inlined into the output by capturing a value in a Html type:

captureValue("Inline HTML" -> Html(<em>Hello!</em>))

All other values are displayed as their String representation, unless a custom renderer has been defined.

Custom Rendering of Interesting Givens & Captured Inputs And Outputs

When you capture a value or an interesting given, it will be rendered to the screen. XML and Strings are formatted nicely by default, but you may wish to capture your own domain objects and have them presented in readable format.

A full example is here: [clairvoyance/specs2/examples/CustomRenderingExample.scala] (https://github.com/rhyskeepence/clairvoyance/blob/master/specs2/src/test/scala/clairvoyance/specs2/examples/CustomRenderingExample.scala)

The juicy bits are shown below:

class CustomRenderingExample extends ClairvoyantSpec with CustomRendering {

  def customRendering = {
    case Brain(iq) => "a Brain with an IQ of %d".format(iq)

customRendering is a partial function, which will be run before the default rendering.

And behold, custom rendering of Brains:

Custom Rendering of Brains

Sequence Diagrams

If your spec describes interactions between many systems, it can be nice to generate a sequence diagram automatically from CapturedInputsAndOutputs. Just add the SequenceDiagram trait to your context, ie:

trait context extends ClairvoyantContext with SequenceDiagram {
  override def capturedInputsAndOutputs = Seq(system_x, system_y)

The name of the captured values should be in the following formats in order to appear on the diagram:

captureValue("SOMETHING from X to Y" -> ...) or

captureValue("SOMETHING from X" -> ...) or

captureValue("SOMETHING to Y" -> ...)

In the last two cases, the default actor will be used, which can be set using this statement in the context: override def defaultSequenceDiagramActor = "Name of my component"

An example can be found here, which produces the following output:

Sequence Diagram

Alternatively, a graph can be produced:

trait context extends ClairvoyantContext with Graph


Markdown is supported in specification descriptions, to whet your appetite see this example.



  • Scenario tables