> ## Documentation Index > Fetch the complete documentation index at: https://mehen.ophi.dev/llms.txt > Use this file to discover all available pages before exploring further. # Supported formats > The six coverage-report formats mehen parses — LCOV, Go coverprofile, Istanbul JSON, JaCoCo XML, Clover XML, Cobertura XML — and how they are detected and merged. mehen parses six report formats in-house — no external tools, no network — covering the default or one-flag-away output of the mainstream test runners in every language mehen analyzes. The parsers are streaming (large monorepo reports never sit fully in memory) and were adapted from the MIT-licensed [covrs](https://github.com/scttnlsn/covrs) project. ## The formats | Format | Shape | Typical producers | Dimensions | | ------------------- | --------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------- | | **LCOV** | line records (`SF:`/`DA:`/`BRDA:`/`FN:`) | cargo-llvm-cov, tarpaulin, `lcov`/`geninfo` (C/C++), Jest & c8 & nyc (`lcov` reporter), simplecov-lcov (Ruby), coverlet (`lcov` format), coverage.py (`coverage lcov`) | line, branch, function | | **Go coverprofile** | `mode:` header + per-block ranges | `go test -coverprofile` | line | | **Istanbul JSON** | `statementMap`/`branchMap`/`fnMap` objects | Jest, Vitest, nyc, c8 (`coverage-final.json`) | line, branch, function | | **JaCoCo XML** | `` → `` → `` | JaCoCo (Maven/Gradle), Kotlin Kover, Pester 5 (PowerShell) | line, branch, function | | **Clover XML** | `` → `` → `` | PHPUnit, OpenClover, Jest/Vitest (`clover` reporter) | line, branch (from `cond` lines), function (from `method` lines) | | **Cobertura XML** | `` → `` | coverage.py (`coverage xml`), coverlet / `dotnet test`, gcovr, tarpaulin (`--out xml`) | line, branch (from `condition-coverage`), function (from ``) | ## Detection is content-based Filenames lie: Pester writes JaCoCo XML into `coverage.xml`, coverage.py writes Cobertura XML into the same name, and `.info` files are occasionally GNU documentation. mehen therefore *sniffs* the first 4 KiB of every candidate and requires format-specific content markers before believing a file, in a fixed priority order chosen so no format can false-positive on another's output: 1. **LCOV** — `SF:` plus `DA:`/`FN:` records. 2. **Go coverprofile** — a `mode: set|count|atomic` header or `file.go:N.N,N.N …` block lines. 3. **Istanbul** — a JSON object containing `"statementMap"` and `"fnMap"`. 4. **JaCoCo** — `` argument goes through the same detection; a file no parser recognizes is a hard error, while an auto-discovered candidate that fails sniffing is silently recorded as rejected (that is business as usual for e.g. `coverage.txt` text summaries). ## Normalization and merge semantics Formats disagree about granularity, so parsed records are normalized into one model — per-file line hits, branch arms, and function records: * **Statements → lines.** Istanbul statements and Go blocks map onto lines; when several statements share a line, the *maximum* hit count wins. * **Branch encodings → arms.** LCOV `BRDA` records, Cobertura `condition-coverage="50% (1/2)"` fractions, JaCoCo `mb`/`cb` counters, Clover `truecount`/`falsecount` pairs, and Istanbul `b` arrays all become flat *branch arms* (see [branch coverage](/metrics/coverage/branch) for what that folding means). * **Duplicate records collapse.** `lcov -a`-merged tracefiles repeat `DA` lines; Cobertura emits the same line under both `` and `` — duplicates keep the maximum. * **Cross-report merge.** All ingested reports fold into one dataset: union of files, saturating-max hits for records shared between reports ("covered anywhere ⇒ covered"). Max is commutative and associative, so the merged result is independent of discovery order — determinism is a hard requirement for reproducible CI gates. Hit-count *summing* was rejected because re-running the same suite twice would double every count; newest-file-wins was rejected because git checkouts do not preserve mtimes. ## Hardening Coverage artifacts are ingested from build directories that other tools write into, so the parsers are defensive by construction: branch expansion is capped at 1,024 arms per line, Go block spans at 100,000 lines, report files at 256 MiB; XML parsing never resolves DTDs or external entities (billion-laughs and XXE are structurally inert, and a regression test pins that); and a malformed report is a per-file diagnostic, never a crash. ## What about raw instrumentation output? `.profraw`/`.gcda` (LLVM/GCC counters), SimpleCov's `.resultset.json`, c8's raw V8 dumps in `coverage/tmp/`, and coverlet's proprietary `coverage.json` are *not* report formats — decoding them requires the compiled binaries or the producing tool's internals. Export a report instead (`cargo llvm-cov --lcov`, `coverage xml`, `--coverageReporters=lcov`, …); grcov takes the same report-level stance for Firefox-scale ingestion. ## References * [geninfo(1) — the LCOV tracefile format](https://ltp.sourceforge.net/coverage/lcov/geninfo.1.php). *Linux Test Project.* * [The cover story](https://go.dev/blog/cover) — Go's coverage design and the coverprofile format. *The Go Blog.* * [Istanbul.js](https://istanbul.js.org/) and the [istanbuljs coverage object](https://github.com/istanbuljs/istanbuljs). * [JaCoCo XML report documentation](https://www.jacoco.org/jacoco/trunk/doc/). * [OpenClover documentation](https://openclover.org/documentation) — the Clover XML schema. * [Cobertura](https://cobertura.github.io/cobertura/) — the original tool whose XML schema became the de-facto interchange format. * [mozilla/grcov](https://github.com/mozilla/grcov) — prior art for multi-format coverage aggregation at scale.