Friday, 28 October 2016

Configuring Jacoco4sbt for a Play application

Despite (or perhaps due to) my recent dalliances with React.js, I'm still really loving the Play Framework, in both pure-backend- (JSON back-and-forth) and full-stack (serving HTML) modes. It's had a tremendous amount of thought put into it, it's been rock-solid in every situation (both work- and side-project) I've deployed it, it's well-documented and there's a solid ecosystem of supporting plugins, frameworks and libraries available.

One such plugin is Jacoco4sbt, which wires the JaCoCo code-coverage tool into SBT (the build system for Play apps). Configuration is pretty straightforward, and the generated HTML report is a nice way to target untested corners of your code. The only downside (which I've finally got around to looking at fixing) was that by default, a lot of framework-generated code is included in your coverage stats.

So without further ado, here's a stanza you can add to your Play app's build.sbt to whittle down your coverage report to code you actually wrote:

jacoco.settings

jacoco.excludes in jacoco.Config := Seq(
    "views*",
    "*Routes*",
    "controllers*routes*",
    "controllers*Reverse*",
    "controllers*javascript*",
    "controller*ref*",
    "assets*"
)
I'll be putting this into all my Play projects from now on. Hope it helps someone.

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