mutation-testing-metrics-scala

Mutation testing metrics (Scala)

Zero-dependency library to calculate mutation testing metrics in Scala.

See mutant states and metrics in the Stryker handbook for more details about mutation testing metrics.

Cross-compiled for Scala 2.12, 2.13, Dotty, Scala.js 0.6.x and Scala Native 0.3.x.

Usage example

Add the dependency to your project :

libraryDependencies += "io.stryker-mutator" %% "mutation-testing-metrics" % version

If you use Scala.js or Scala Native, use %%% instead after the groupId.

First create the mutation test report:

import mutationtesting._
val report = MutationTestReport(thresholds = Thresholds(high = 80, low = 10),
  files = Map(
    "src/stryker4s/Stryker4s.scala" -> MutationTestResult(
      source = "case class Stryker4s(foo: String)",
      mutants = Seq(
        MutantResult("1", "BinaryOperator", "-", Location(Position(1, 2), Position(2, 3)), status = MutantStatus.Killed)
      )
    )
  )
)

The MutationTestReport case classes generate a JSON compliant with the mutation-testing JSON schema.

Then calculate and use metrics from that report:

val metrics: MetricsResult = Metrics.calculateMetrics(report)

That report will have all the metrics you need:

val mutationScore = metrics.mutationScore
// mutationScore: Double = 70.12987012987013
val killed = metrics.killed
// killed: Int = 162
val survived = metrics.survived
// survived: Int = 69

mutation-testing-metrics-circe

Circe transcodings are provided by the mutation-testing-metrics-circe library to work with JSON if you don't want the extra dependency on circe-generic. It has two dependencies: circe-core and circe-parser.

libraryDependencies += "io.stryker-mutator" %% "mutation-testing-metrics-circe" % version

Encoding

Import the encoder:

import io.circe.syntax._
import mutationtesting.MutationReportEncoder._

val encoded = report.asJson

Decoding

Import the decoder:

import io.circe.parser.decode
import mutationtesting.MutationReportDecoder._

val decoded = decode[MutationTestReport](json)

API reference

MetricsResult

A MetricsResult has the following properties, as described in the handbook:

metrics.killed
// res1: Int = 162
metrics.survived
// res2: Int = 69
metrics.timeout
// res3: Int = 0
metrics.noCoverage
// res4: Int = 0
metrics.compileErrors
// res5: Int = 0
metrics.totalDetected
// res6: Int = 162
metrics.totalUndetected
// res7: Int = 69
metrics.totalCovered
// res8: Int = 231
metrics.totalValid
// res9: Int = 231
metrics.totalInvalid
// res10: Int = 0
metrics.totalMutants
// res11: Int = 231
metrics.mutationScore
// res12: Double = 70.12987012987013
metrics.mutationScoreBasedOnCoveredCode
// res13: Double = 70.12987012987013

• MetricsResult is a trait with three implementations:
  • MetricsResultRoot: The root of a MetricsResult, contains zero or more MetricsResult's
  • MetricsDirectory: Representation of a directory. Has a directory name and zero or more MetricsResult's
  • MetricsFile: Representation of a file with mutated code. Has a filename and zero or more MetricMutant's
• MetricMutant: Contains a MutantStatus

Contributing

To use this project, you will need sbt. The recommended way on macOS/Linux is with sbt-extras. On Windows, you can install sbt using the official .msi.

This project uses the sbt-crossproject plugin for multiple build targets. You can compile code with sbt compile and run tests with sbt test. Running sbt +test will compile and test all targets.

In CI, JS and Native will only be compiled, while tests are run on the JVM project to provide faster CI builds. Publishing is done on all targets. For more information on cross-compilation in sbt, see https://www.scala-sbt.org/1.x/docs/Cross-Build.html.

This readme uses mdoc. To edit it, please edit the readme in docs and call sbt docs/mdoc to compile the readme in the root of the project.

Changelog

1.2.3 (2019-12-11)

Note: Version bump only for package root