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Coverage

Beyond pass/fail assertions, Hop JUnit measures scope coverage: which transforms and hops (Edges) of your pipelines and workflows your JUnit executions actually traversed. This is a graph coverage of the Hop artifacts, not a Java code-coverage metric.

How it works

  1. A LauncherSessionListener is registered automatically through the standard JUnit service loader mechanism (META-INF/services/org.junit.platform.launcher.LauncherSessionListener), so adding hop-junit-core to the test classpath is enough.

  2. When coverage is enabled (hop.coverage.enabled=true, the default), every @HopPipeline / @HopWorkflow execution attaches a collector to the Hop engine and records nodes (transforms), edges (hops) and row counters.

  3. Pipelines executed nested inside workflows are captured by a Hop extension point (PipelineCoverageExtensionPoint, registered idempotently when the runtime starts) and deduplicated, so a pipeline run standalone and nested still counts its nodes once.

  4. When the JUnit session closes, the runtime writes a raw JSON report and the post-processor merges the executions, applies the required-coverage thresholds and renders the configured formats.

Configuration

All knobs are system properties, typically set from the surefire plugin:

Property Default Description

hop.coverage.enabled

true

Enable collection and reporting.

hop.coverage.basedir

.

Base directory paths are reported relative to.

hop.coverage.workDir

target/hop-coverage

Working directory for raw executions.

hop.coverage.rawDir

<workDir>/raw

Where the per-JVM raw JSON reports are written.

hop.coverage.siteDir

target/hop-coverage/report

Where the rendered reports are written.

hop.coverage.report.format

JSON,HTML,ADOC

Comma-separated list of JSON, HTML, ADOC.

hop.coverage.requiredCoverage

unset

Global required coverage in percent (e.g. 80).

hop.coverage.requiredCoverage.<ARTIFACT>

global value

Per-artifact override, e.g. hop.coverage.requiredCoverage.T_LOAD=66.0 (artifact name without extension).

hop.coverage.failOnMalformedReport

true

Fail the build when a raw report is malformed.

hop.coverage.failOnWriteError

true

Fail the build when a report cannot be written.

hop.report.adoc.output

target/hop-coverage/report/coverage.adoc

Where the ADOC report is written (include it in your own docs with include::).

Enforcing thresholds

Declare the global threshold and, when needed, per-artifact overrides, and propagate them to the test JVM: 

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <configuration>
    <systemPropertyVariables>
      <hop.coverage.enabled>true</hop.coverage.enabled>
      <hop.coverage.basedir>${project.basedir}</hop.coverage.basedir>
      <hop.coverage.requiredCoverage>80</hop.coverage.requiredCoverage>
      <hop.coverage.requiredCoverage.T_LOAD>66.0</hop.coverage.requiredCoverage.T_LOAD>
    </systemPropertyVariables>
  </configuration>
</plugin>

A pipeline or workflow whose coverage is below its threshold fails the build after the test run.

Rendering reports

With hop.coverage.report.format=JSON,HTML,ADOC, the session close produces:

  • a machine-readable JSON report under hop.coverage.rawDir (one per JVM, merged by the post-processor),

  • an HTML report under hop.coverage.siteDir,

  • an ADOC report written to hop.report.adoc.output (default target/hop-coverage/report/coverage.adoc), designed to be pulled into your own AsciiDoc documentation with a standard include directive pointing at that generated file.

Metrics

For each execution Hop JUnit records:

  • nodes - every transform of the pipeline/workflow, with started/finished copies, input/output/ read/written rows and errors, and whether it was covered (started, finished, or inferred as processing rows);

  • edges - every hop between transforms, with the transferred row count and whether it was traversed;

  • summary - node coverage ratio, edge coverage ratio and branch coverage ratio (an edge is a branch when its source transform has several enabled outgoing edges);

  • run - the JUnit test (class, method, display name, unique id) and the timing of the execution.

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