mockymock for VS Code

Download the .vsix and install it in VS Code to start unit-testing your COBOL today — see you on the wildside.

Why mockymock

Unit testing and debugging COBOL is normally gated behind provisioning a z/OS environment — infrastructure that can run into the hundreds of thousands of dollars for something that's standard, free tooling in every other language thank you IBM. mockymock's goal is to close that gap: a fast, local and simple unit-testing and debugging loop for COBOL — write a .cut suite, mock out the file I/O, CICS, DB2, IMS, and MQ boundaries, vola you're good to go. No mainframe access required and no hassel, good vibration guaranteed.

The idea started from cobol-check, the open-source COBOL unit-testing framework, but mockymock was rebuilt from the ground up with its own .cut syntax, mocking model, coverage/trace tooling, and interactive debugger. mockymock's own CLI source lives in a private repository, so this extension repo — its .cut language, the examples/ below, and this README — is the reference for what it does and how to use it.

Features

• Test Explorer tree for every .cut file, with tag filtering.
• Run single tests or subsets, including "rerun failed."
• Failures land on the failing line, with an expected/actual diff.
• Coverage painted on your original .cbl gutter.
• Debug (Execution Trace) — see the executed path and mocks that fired.
• Debug (Interactive) — real breakpoints, stepping, and variable inspection on your original .cbl.
• Continuous run — re-run a test automatically on file change.
• Cancellation that actually kills the in-flight run.
• Live linting on open/save, zero Docker needed.
• .cut language support — syntax highlighting, folding, snippets.
• Export Mainframe-Ready COBOL — write the instrumented build to a real fixed-format .cbl, adjusted for a mainframe (z/OS) COBOL compiler instead of GnuCOBOL, zero Docker needed.
• Environment bootstrap — auto-installs the CLI and starts Docker Desktop for you, with a status bar item to check or retry.
• No silent failures — anything mockymock can't attribute to a test case still surfaces as an error, not a false green.

Compiler

mockymock compiles and runs your COBOL with GnuCOBOL, not an IBM Enterprise COBOL compiler. GnuCOBOL is close enough for most day-to-day unit testing, but it's a different compiler with its own dialect quirks, extensions, and gaps versus IBM's mainframe compiler — some IBM-only syntax or behavior may not compile or may behave differently under mockymock. Treat green tests here as strong local signal, not a guarantee that the same source will compile and behave identically on z/OS.

Compiling and running tests directly against a mainframe/IBM COBOL compiler is on the roadmap.

Install

Download the .vsix matching your OS from this repo's Releases page, then install it:

code --install-extension mockymock-vscode-<platform>-<version>.vsix

Or download from the microsoft extension store (currently worked on)

Settings

Requirements

• The mockymock CLI. Official release .vsix packages (see Install above) already bundle a matching binary — nothing to install. Otherwise (running from source, or on a platform with no bundled binary) it's auto-installed via uv on first run if missing. Single-test runs, tags, lint, JSON reports, and coverage mapping need a CLI new enough to have collect/lint/--case/--json-report/--coverage-json; older CLIs degrade gracefully (whole-file runs, JUnit results, regex discovery). Debug (Execution Trace) additionally needs --trace-json; Debug (Interactive) needs the debug subcommand; Export Mainframe-Ready COBOL needs the export subcommand. An older CLI degrades to a clear message on the one feature it affects rather than failing anything else.
• Docker (mockymock compiles and runs COBOL in its mockymock-cobc container). If Docker Desktop is installed but not running, the extension starts it automatically before your first run/lint and waits for it to become ready — no need to launch it yourself. If Docker isn't installed at all, you'll get a prompt linking to the Docker Desktop download page.
• VS Code ≥ 1.88.

Examples

examples/ has 13 worked COBOL programs, copied from mockymock's own test suite so they're here even though the CLI's source repo is private. Each proves a boundary category compiles and runs for real under GnuCOBOL, and each has its own README plus a runnable .cut:

mockymock run examples/invupdt/INVUPDT.cbl --cut examples/invupdt/INVUPDT.cut

(Examples under copybooks/ — cpyproc, custprog, and everything under real-world/ — need a --copybook-path examples/<name>/copybooks flag too; see that example's own README.)

• ordrproc — the minimal case: one external subprogram CALL.
• raterte — dynamic CALL through a variable holding the program name ("poor man's polymorphism").
• invupdt — every boundary category in one program: file I/O, a DB2 UPDATE, an MQ CALL, and operator ACCEPT.
• custinq — a CICS transaction (EXEC CICS READ/RETURN), no CICS translator needed.
• custprog — DB2 cursors (DECLARE/OPEN/FETCH/CLOSE) and DCLGEN-style copybook host variables.
• claimseg — IMS DL/I segment retrieval and insert (EXEC DLI GU/ISRT).
• cpyproc — a shared paragraph pulled in via a COPY copybook, tested directly and as a stubbed collaborator.
• flowmock — mocking an internal paragraph or section directly, not just external calls.
• regnavg — subscripted tables, REDEFINES, DIVIDE ROUNDED, and --trace output.
• statelkup — data-driven cases: one TESTCASE ... USING PROVIDER row-expands into many.
• taxfile — shared BEFORE-EACH mocks that individual cases override.
• nist-cobol85 — unmodified programs from the public-domain NIST COBOL-85 validation suite.
• real-world — four production-shaped programs: an IMS DL/I batch purge, an IMS MPP deposit transaction (also the coverage-reporting worked example), and an MQ producer/consumer pair with two-phase DB2 commit.

License

GPL-3.0. This covers this extension repo (the .cut language tooling, examples, and docs here) — the mockymock CLI itself lives in a separate, private repository and is not covered by this license.