diff --git a/.github/workflows/verify.yml b/.github/workflows/verify.yml
new file mode 100644
index 0000000..f090d32
--- /dev/null
+++ b/.github/workflows/verify.yml
@@ -0,0 +1,27 @@
+name: Verify
+
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  verify:
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v7
+
+      - name: Build generated scripts
+        run: make -B all
+
+      - name: Run verification
+        run: make verify
+
+      - name: Check for generated diffs
+        run: git diff --exit-code
diff --git a/Makefile b/Makefile
index 897bfde..33f5da1 100644
--- a/Makefile
+++ b/Makefile
@@ -1,9 +1,12 @@
 SOURCES = bj.sh rollup.rb linebreak.rb
 TARGETS = bj-1line.sh bj-80-col.sh bj-90-col.sh
 
-.PHONY: all
+.PHONY: all verify
 all: $(TARGETS)
 
+verify:
+	./verify.sh
+
 $(TARGETS): $(SOURCES)
 
 bj-1line.sh:
diff --git a/README.md b/README.md
index 4820798..c4d0eed 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,5 @@
+[![Yes, this bizarre 863-byte Bash JSON parser is actually tested.](https://github.com/memotype/bj.sh/actions/workflows/verify.yml/badge.svg)](https://github.com/memotype/bj.sh/actions/workflows/verify.yml)
+
 bj.sh is a pure GNU Bash library for parsing JSON data.
 
 bj.sh is meant to be run as a script, sourced as a library, or copied directly
diff --git a/verify.sh b/verify.sh
new file mode 100755
index 0000000..5aa1880
--- /dev/null
+++ b/verify.sh
@@ -0,0 +1,105 @@
+#!/usr/bin/env bash
+
+cd -- "$(dirname -- "${BASH_SOURCE[0]}")" || exit 1
+
+fail() {
+  echo "VERIFY FAIL: $*" >&2
+  exit 1
+}
+
+generated=(bj-1line.sh bj-80-col.sh bj-90-col.sh)
+implementations=(bj.sh "${generated[@]}")
+executables=(bj.sh test.sh verify.sh rollup.rb linebreak.rb "${generated[@]}")
+
+echo "Checking syntax and executable modes"
+bash -n bj.sh test.sh verify.sh "${generated[@]}" \
+  || fail "Bash syntax check failed"
+ruby -c rollup.rb || fail "rollup.rb syntax check failed"
+ruby -c linebreak.rb || fail "linebreak.rb syntax check failed"
+
+for file in "${executables[@]}"; do
+  [[ -x $file ]] || fail "$file is not executable"
+done
+
+echo "Checking bj.sh CLI"
+output=$(./bj.sh '{"foo":"bar"}' foo)
+status=$?
+[[ $output = bar && $status = 0 ]] || fail "bj.sh CLI query failed"
+
+output=$(printf %s '{"foo":"bar"}' | ./bj.sh - foo)
+status=$?
+[[ $output = bar && $status = 0 ]] || fail "bj.sh CLI stdin query failed"
+
+output=$(./bj.sh '{"foo":"bar"}' missing)
+status=$?
+[[ -z $output && $status = 1 ]] \
+  || fail "bj.sh CLI missing-query status failed"
+
+echo "Checking generated files"
+verify_dir=$(mktemp -d) || fail "Could not create temporary directory"
+trap 'rm -r -- "$verify_dir"' EXIT
+
+./rollup.rb bj.sh "$verify_dir/bj-1line.sh" \
+  || fail "Could not regenerate bj-1line.sh"
+./linebreak.rb --max-lines 13 80 \
+  "$verify_dir/bj-1line.sh" "$verify_dir/bj-80-col.sh" \
+  || fail "Could not regenerate bj-80-col.sh"
+./linebreak.rb --max-lines 12 90 \
+  "$verify_dir/bj-1line.sh" "$verify_dir/bj-90-col.sh" \
+  || fail "Could not regenerate bj-90-col.sh"
+
+for file in "${generated[@]}"; do
+  diff -u "$file" "$verify_dir/$file" \
+    || fail "$file differs from regenerated output"
+done
+
+awk '!/^#/ { code++ } END {
+  if (NR != 2 || code != 1) {
+    print FILENAME ": expected one header and one code line" > "/dev/stderr"
+    exit 1
+  }
+}' bj-1line.sh || fail "bj-1line.sh is not the canonical one-line form"
+
+check_wrapped() {
+  local file=$1 width=$2 max_lines=$3
+
+  awk -v width="$width" -v max_lines="$max_lines" '
+    length > width {
+      printf "%s:%d exceeds %d columns (%d)\n",
+        FILENAME, FNR, width, length($0) > "/dev/stderr"
+      bad=1
+    }
+    !/^#/ { code++ }
+    END {
+      if (code > max_lines) {
+        printf "%s has %d code lines; maximum is %d\n",
+          FILENAME, code, max_lines > "/dev/stderr"
+        bad=1
+      }
+      exit bad
+    }
+  ' "$file" || fail "$file violates its wrapping constraints"
+}
+
+check_wrapped bj-80-col.sh 80 13
+check_wrapped bj-90-col.sh 90 12
+
+run_functional_tests() {
+  local label=$1
+  shift
+
+  echo "Functional tests ($label)"
+  for implementation in "${implementations[@]}"; do
+    "$@" ./test.sh -s "./$implementation" \
+      || fail "$implementation failed under $label"
+  done
+}
+
+run_functional_tests "the default locale"
+run_functional_tests "LC_ALL=C" env LC_ALL=C
+
+echo "Checking diffs"
+git diff --check || fail "Unstaged changes contain whitespace errors"
+git diff --cached --check || fail "Staged changes contain whitespace errors"
+
+echo "Verification passed"