Jest coverage from one or multiple files

.bashrc

# Function: jestCoverage
# Description:
#   Runs Jest with coverage enabled. It automatically maps .spec.ts files
#   to their corresponding .ts source files for --collectCoverageFrom.
jestCoverage() {
    if [[ $# -eq 0 ]]; then
        echo "Error: No arguments provided." >&2
        echo "Usage: jestCoverage [jest-flags] <file1.spec.ts> [file2.spec.ts ...]" >&2
        return 1
    fi

    local spec_files=()
    local ts_files=()
    local other_args=()
    local base

    # Iterate through all arguments to categorize them
    for arg in "$@"; do
        if [[ "$arg" == *.spec.ts ]]; then
            spec_files+=("$arg")
            # Derive the source file name (e.g., app.spec.ts -> app.ts)
            base="${arg%.spec.ts}"
            ts_files+=("${base}.ts")
        else
            # This captures flags like --watch, --updateSnapshot, or --config
            other_args+=("$arg")
        fi
    done

    # Safety check: Ensure we actually found spec files
    if [[ ${#spec_files[@]} -eq 0 ]]; then
        echo "Error: No .spec.ts files were identified in the arguments." >&2
        return 1
    fi

    # Build a single brace-expansion glob for --collectCoverageFrom.
    # e.g. one file: "src/foo/bar.ts"  multiple: "{src/foo/bar.ts,src/baz/qux.ts}"
    local IFS=','
    local coverage_glob
    if [[ ${#ts_files[@]} -eq 1 ]]; then
        coverage_glob="${ts_files[0]}"
    else
        coverage_glob="{${ts_files[*]}}"
    fi
    unset IFS

    # Construct command array for safe execution (no eval needed)
    # Order: pnpm jest [coverage-flags] [other-args] [test-files]
    local cmd=(
        "pnpm"
        "jest"
        "--coverage"
        "--collectCoverageFrom" "${coverage_glob}"
        "${other_args[@]}"
        "${spec_files[@]}"
    )

    # Execute the command array directly
    echo "Executing: ${cmd[*]}"
    "${cmd[@]}"
}

alias jestc='jestCoverage'

jest-coverage.nu

# Function: jestCoverage
# Description:
#   Runs Jest with coverage enabled. It maps .spec.ts files
#   to corresponding .ts files for --collectCoverageFrom.
export def jestCoverage [...args: string] {
    if ($args | is-empty) {
        error make { msg: "No arguments provided. Usage: jestCoverage [jest-flags] <file1.spec.ts> [file2.spec.ts ...]" }
    }

    mut spec_files = []
    mut ts_files = []
    mut other_args = []

    for arg in $args {
        if ($arg | str ends-with ".spec.ts") {
            $spec_files = ($spec_files | append $arg)
            let base = ($arg | str replace --regex '\.spec\.ts$' '')
            $ts_files = ($ts_files | append ($base + ".ts"))
        } else {
            $other_args = ($other_args | append $arg)
        }
    }

    if (($spec_files | length) == 0) {
        error make { msg: "No .spec.ts files were identified in the arguments." }
    }

    let coverage_glob = if (($ts_files | length) == 1) {
        $ts_files.0
    } else {
        "{" + ($ts_files | str join ",") + "}"
    }

    let cmd_preview = (
        ["pnpm" "jest" "--coverage" "--collectCoverageFrom" $coverage_glob]
        ++ $other_args
        ++ $spec_files
    )

    print $"Executing: ($cmd_preview | str join ' ')"

    ^pnpm jest --coverage --collectCoverageFrom $coverage_glob ...$other_args ...$spec_files
}

export alias jestc = jestCoverage

usage.md

Jest coverage

Bash/Zsh and Nushell scripts for targeting Jest coverage to one or more files with flag support for watching the files etc.

Bash

How to use it with Bash/Zsh:

1. Copy the content of the first file to your .bashrc or .zshrc
2. Open a new terminal
3. Run jestc src/test-file.spec.ts or jestc --watch src/test-file-1.spec.ts src/test-file-2.spec.ts

Nushell

How to use it with Nushell:

1. Save the contents of the .nu file to something like scripts/jest-coverage.nu
2. Load it in Nushell:

use scripts/jest-coverage.nu *

3. Open a new terminal
4. Run jestc src/test-file.spec.ts or jestc --watch src/test-file-1.spec.ts src/test-file-2.spec.ts