Code coverage with Testo

Coverage is opt-in via the CodecovPlugin in testo.php. The plugin needs:

1. A coverage level — Line, Branch, or Path (each adds cost and information).
2. One or more report writers — Clover, Cobertura, PHPUnit XML.
3. Xdebug ≥ 3.1 (in coverage mode) or PCOV available on the runner. Without one of them, the plugin will skip. The coverage mode can be set via xdebug.mode=coverage, the -d xdebug.mode=coverage CLI flag, or the XDEBUG_MODE=coverage env var — Testo resolves the active mode with xdebug_info('mode'), so the env override (used by composer infect and IDE coverage runners) counts.

Fetch https://php-testo.github.io/llms.txt (and llms-full.txt if you need plugin wiring detail) before editing — exact class names and constructor parameters are authoritative there.

Canonical wiring in testo.php

use Testo\Application\Config\ApplicationConfig;
use Testo\Codecov\CodecovPlugin;
use Testo\Codecov\Config\CoverageLevel;
use Testo\Codecov\Report\CloverReport;
use Testo\Codecov\Report\CoberturaReport;
use Testo\Codecov\Report\PhpUnitXmlReport;

return new ApplicationConfig(
    src: ['src'],
    suites: [/* ... */],
    plugins: [
        new CodecovPlugin(
            level: CoverageLevel::Line,
            reports: [
                new CloverReport(__DIR__ . '/runtime/clover.xml', 'MyProject'),
                new CoberturaReport(__DIR__ . '/runtime/cobertura.xml'),
                new PhpUnitXmlReport(outputDir: __DIR__ . '/runtime/coverage-xml'),
            ],
        ),
    ],
);

Then enable on the CLI:

vendor/bin/testo --coverage
vendor/bin/testo --no-coverage   # explicit off, overrides config

--coverage makes coverage mandatory (CoverageMode::Always): the run aborts with CoverageDriverNotAvailable (non-zero exit) when no Xdebug/PCOV driver is present — even with no report flags. That makes a bare vendor/bin/testo --coverage a handy CI gate to assert the driver is actually available. --no-coverage always wins over everything.

CLI report flags (no testo.php needed)

A CodecovPlugin ships in the application defaults in shadow (inert) mode, so three flags let external tools (the IDE plugin, Infection) pin report destinations without any testo.php change:

vendor/bin/testo --coverage-clover=build/clover.xml
vendor/bin/testo --coverage-cobertura=build/cobertura.xml
vendor/bin/testo --coverage-xml=build/coverage-xml      # directory, for Infection

• Soft activation. Passing any of these implies coverage collection if a driver is available; with no Xdebug/PCOV the run skips silently (no file). --no-coverage still wins and disables it.
• Parallel with your config. If testo.php already declares a CodecovPlugin, the flag-driven reports run alongside your configured ones — both sets of files are written. The two are merged into a single coverage collection (no double overhead): the deepest requested level wins, test-type filters are unioned, and every report (yours + the CLI ones) is emitted.
• The shadow stays fully inert when no report flag is present, so default behavior is unchanged.

Choosing the level on the CLI

vendor/bin/testo --coverage-level=branch --coverage-clover=build/clover.xml

--coverage-level takes line, branch or path (case-insensitive) and pins the depth for the whole run — it wins over every CodecovPlugin(level: …), including when it asks for less. An unknown value aborts the run rather than falling back.

Without the flag the configured levels are merged and the deepest wins, so a new CodecovPlugin(level: CoverageLevel::Branch) in testo.php still applies to a run that only the CLI report flags activated.

Picking the coverage level

Level	Cost	When
Line	Low	Default for CI gates.
Branch	Medium	When you need to be sure if/match/?: branches are exercised.
Path	High	Mutation testing setup, exhaustive analysis. Usually local-only.

Don't ship Path on every CI run — it's the slowest. Reserve it for mutation testing or scheduled jobs.

With fibers (#[RunInFiber]), use Line only. Branch and Path enable Xdebug's branch analysis, which corrupts memory and crashes the process when it runs inside a fiber — no PHP error, no report. The bug persists in current Xdebug builds (reproduced on 3.5.3). Testo tries to stop such a test with BranchCoverageUnsafeInFiber, but the guard is tied to the Xdebug version and doesn't fire on every build — don't rely on it. PCOV is unaffected (it only does Line anyway).

#[Covers] and #[CoversNothing]

Declare which production classes a test exercises. This scopes coverage reports and surfaces dead tests.

use Testo\Codecov\Covers;
use Testo\Codecov\CoversNothing;

#[Test]
#[Covers(UserService::class)]              // class-level — applies to every test in the class
final class UserServiceTest { /* ... */ }

#[Test]
#[Covers(OrderTotal::class)]
#[Covers(TaxCalculator::class)]            // repeatable: multiple covered targets
final class CheckoutTest { /* ... */ }

#[Test]
#[CoversNothing]                            // explicitly exclude from coverage attribution
final class SmokeTest { /* ... */ }

Rules (this is project policy in many Testo codebases — confirm before changing):

• Class-level #[Covers] when every test in the class covers the same production class. This is the default.
• Method-level #[Covers] when tests in the same class cover different classes.
• Free functions: pass the FQN as a string — #[Covers('App\\helpers\\format_money')] (verify against llms.txt for the version in use).

Reports cheat-sheet

Report	Format id	Typical consumer
CloverReport	clover	Codecov, Coveralls, GitHub coverage diffs.
CoberturaReport	cobertura	GitLab/Jenkins coverage UI.
PhpUnitXmlReport	coverage-xml	Infection (mutation testing).

For Infection, point infection.json's coverage.path at the directory you gave to PhpUnitXmlReport.

Every written report is announced, not printed: the run dispatches Testo\Event\Report\ReportFileGenerating once it knows coverage will be collected and ReportFileGenerated after the file is written, and whichever renderer owns stdout states it — a plain line in a terminal, a ##teamcity[testoReport …] service message under --teamcity. The format id in the table is what a consumer switches on.

CoverageReport therefore has two methods: generate() and info(): ReportInfo (Testo\Core\Report\ReportInfo — format, label, and a Stringable location). The location is what a consumer opens: for a report that fills a directory, the index inside it rather than the directory; for one that uploads its data, whatever URL it lands on.

final readonly class MyReport implements CoverageReport
{
    public function __construct(private string $path) {}

    public function generate(CoverageResult $result): void { /* write $this->path */ }

    public function info(): ReportInfo
    {
        return new ReportInfo('my-format', 'My coverage', Path::create($this->path));
    }
}

Pitfalls

• No coverage written? Check the active Xdebug mode includes coverage — set it via xdebug.mode, -d xdebug.mode=coverage, or XDEBUG_MODE=coverage (or load PCOV). Testo skips the driver if neither is available.
• clover.xml empty? Suite-level finder probably excludes the src directory you expected — verify the FinderConfig covers it.
• Don't enable coverage in benchmark suites — it falsifies timings.
• Coverage under #[RunInFiber] costs an extra driver stop/start per suspension (the window is closed around every fiber switch so each test keeps its own lines). Suspension-heavy tests pay for it — a reason to keep coverage runs on Line and off the interleaving-heavy suites.
• Don't write #[Covers(SomeInterface::class)] — point at concrete classes that own the executable code.
• Don't combine #[Covers] and #[CoversNothing] on the same class/method — pick one.