diff --git a/.github/workflows/pr.yml.not_active b/.github/workflows/pr.yml.not_active
new file mode 100644
index 0000000..591664c
--- /dev/null
+++ b/.github/workflows/pr.yml.not_active
@@ -0,0 +1,36 @@
+name: PR
+
+on:
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-24.04
+
+    steps:
+      - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3
+
+      - uses: leafo/gh-actions-lua@8c9e175e7a3d77e21f809eefbee34a19b858641b
+        with:
+          luaVersion: 5.4
+
+      - uses: leafo/gh-actions-luarocks@97053c556d6ce2c8e26eb7ac93743437c7af7248
+
+      - name: build
+        run: |
+          luarocks install busted
+          luarocks install moonscript
+
+      - name: Run tests for changed/added exercises
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          pr_endpoint=$(jq -r '"repos/\(.repository.full_name)/pulls/\(.pull_request.number)"' "$GITHUB_EVENT_PATH")
+          gh api "$pr_endpoint/files" --paginate --jq '
+              map(
+                select(.filename | match("\\.odin$")) |
+                .filename |
+                match("exercises/practice/([^/]+)/") |
+                .captures[0].string
+              ) | unique[]
+          ' | xargs -r -L1 bin/test-one
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 1052627..874a5df 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -1,39 +1,28 @@
-# This workflow will verify the exercises in the repository.
-#
-# Requires scripts:
-# - bin/verify-exercises
-
 name: Test
 
 on:
   push:
-    branches: [main]
-  pull_request:
-  workflow_dispatch:
+    branches:
+      - main
 
 jobs:
-  verify_exercises:
-    # TODO: replace with another image if required to run the tests (optional)
+  test:
     runs-on: ubuntu-24.04
 
     steps:
-      - name: Checkout repository
-        uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332
+      - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3
+
+      - uses: leafo/gh-actions-lua@8c9e175e7a3d77e21f809eefbee34a19b858641b
+        with:
+          luaVersion: 5.4
 
-      # TODO: setup any tooling that is required to run the tests (optional)
-      # E.g. install a specific version of a programming language
-      # E.g. install packages via apt/apk/yum/etc.
-      # Find GitHub Actions to setup tooling here:
-      # - https://github.com/actions/?q=setup&type=&language=
-      # - https://github.com/actions/starter-workflows/tree/main/ci
-      # - https://github.com/marketplace?type=actions&query=setup
-      # - name: Use <setup tooling>
-      #   uses: <action to setup tooling>
+      - uses: leafo/gh-actions-luarocks@97053c556d6ce2c8e26eb7ac93743437c7af7248
 
-      # TODO: install any dependencies (optional)
-      # E.g. npm install, bundle install, etc.
-      # - name: Install project dependencies
-      #   run: <install dependencies>
+      - name: build
+        run: |
+          luarocks install busted
+          luarocks install moonscript
 
-      - name: Verify all exercises
-        run: bin/verify-exercises
+      - name: test
+        run: |
+          bin/test-all
diff --git a/bin/add-practice-exercise b/bin/add-practice-exercise
index 7c86306..d097a86 100755
--- a/bin/add-practice-exercise
+++ b/bin/add-practice-exercise
@@ -20,7 +20,7 @@ help_and_exit() {
     echo >&2 "Scaffold the files for a new practice exercise."
     echo >&2 "Usage: ${scriptname} [-h] [-a author] [-d difficulty] <exercise-slug>"
     echo >&2 "Where: author is the GitHub username of the exercise creator."
-    echo >&2 "Where: difficulty is between 1 (easiest) to 10 (hardest)."
+    echo >&2 "     : difficulty is between 1 (easiest) to 10 (hardest)."
     exit 1
 }
 
@@ -37,6 +37,7 @@ require_files_template() {
 }
 
 required_tool jq
+required_tool curl
 
 require_files_template "solution"
 require_files_template "test"
@@ -45,7 +46,7 @@ require_files_template "example"
 [[ -f ./bin/fetch-configlet ]] || die "Run this script from the repo's root directory."
 
 author=''
-difficulty='1'
+difficulty='4'
 while getopts :ha:d: opt; do
     case $opt in
         h) help_and_exit ;;
@@ -59,6 +60,7 @@ shift "$((OPTIND - 1))"
 (( $# >= 1 )) || help_and_exit
 
 slug="${1}"
+snake_slug=${1//-/_}
 
 if [[ -z "${author}" ]]; then
     read -rp 'Your GitHub username: ' author
@@ -67,18 +69,71 @@ fi
 ./bin/fetch-configlet
 ./bin/configlet create --practice-exercise "${slug}" --author "${author}" --difficulty "${difficulty}"
 
+filter='.exercises.practice |= sort_by(.difficulty, (.name|ascii_upcase))'
+jq "${filter}" config.json > config.sorted && mv config.sorted config.json
+
 exercise_dir="exercises/practice/${slug}"
-files=$(jq -r --arg dir "${exercise_dir}" '.files | to_entries | map({key: .key, value: (.value | map("'"'"'" + $dir + "/" + . + "'"'"'") | join(" and "))}) | from_entries' "${exercise_dir}/.meta/config.json")
+files=$(
+    jq -r --arg dir "${exercise_dir}" --arg q "'" '
+        .files
+        | to_entries
+        | map({key: .key, value: (.value | map($q + $dir + "/" + . + $q) | join(" and "))})
+        | from_entries
+    ' "${exercise_dir}/.meta/config.json"
+)
+
+cp exercises/practice/hello-world/.busted "exercises/practice/${slug}/.busted"
+
+mkdir -p canonical-data
+github="https://raw.githubusercontent.com/exercism/problem-specifications/refs/heads/main/exercises/${slug}/canonical-data.json"
+
+curl -s -o "canonical-data/${slug}.json" "$github"
+
+
+camel_slug=$(perl -pe 's/(?:^|-)([a-z])/\u$1/g' <<< "$slug")
+cat << SPEC_GENERATOR > exercises/practice/${slug}/.meta/spec_generator.moon
+{
+  module_name: '${camel_slug}',
+  -- or, module_imports: {'func1', 'func2', ...},
+
+  -- optional:
+  test_helpers: [[
+  A block of code here, indented 2 spaces
+]]
+
+  generate_test: (case, level) ->
+    local lines
+    -- you may want to "switch case.property" here
+    lines = {
+      "result = ${camel_slug}.#{case.property} #{case.input}",
+      "expected = #{quote case.expected}",
+      "assert.are.equal expected, result"
+    }
+    table.concat [indent line, level for line in *lines], '\n'
+}
+SPEC_GENERATOR
+
 
 cat << NEXT_STEPS
 
 Your next steps are:
-- Create the test suite in $(jq -r '.test' <<< "${files}")
-  - The tests should be based on the canonical data at 'https://github.com/exercism/problem-specifications/blob/main/exercises/${slug}/canonical-data.json'
-  - Any test cases you don't implement, mark them in 'exercises/practice/${slug}/.meta/tests.toml' with "include = false"
-- Create the example solution in $(jq -r '.example' <<< "${files}")
-- Verify the example solution passes the tests by running 'bin/verify-exercises ${slug}'
-- Create the stub solution in $(jq -r '.solution' <<< "${files}")
-- Update the 'difficulty' value for the exercise's entry in the 'config.json' file in the repo's root
-- Validate CI using 'bin/configlet lint' and 'bin/configlet fmt'
+
+1.  Create the test suite ==>  $(jq -r '.test' <<< "${files}")
+
+    - A stub test generator awaits you -->  'exercises/practice/${slug}/.meta/spec_generator.moon'
+        - If you don't want it, delete it.
+        - Otherwise, populate it and run it -->  $ bin/generate-spec ${slug}
+
+    - The tests should be based on the canonical data -->  ./canonical-data/${slug}.json
+    - Any test cases you don't implement, mark them in 'exercises/practice/${slug}/.meta/tests.toml' with "include = false"
+
+2.  Create the example solution ==>  $(jq -r '.example' <<< "${files}")
+
+3.  Verify the example solution passes the tests ==>  $ bin/test-one ${slug}
+
+4.  Create the stub solution ==>  $(jq -r '.solution' <<< "${files}")
+
+5.  Update the 'difficulty' value for the exercise's entry in the 'config.json' file in the repo's root
+
+6.  Validate CI using 'bin/configlet lint' and 'bin/configlet fmt'
 NEXT_STEPS
diff --git a/bin/generate-spec b/bin/generate-spec
new file mode 100755
index 0000000..eff7614
--- /dev/null
+++ b/bin/generate-spec
@@ -0,0 +1,128 @@
+#!/usr/bin/env moon
+-- ref: https://github.com/exercism/lua/blob/main/bin/generate-spec
+
+require 'moonscript'
+json = (require 'dkjson').use_lpeg!
+-- import p from require 'moon'
+
+local exercise_name, exercise_directory, spec_generator, included_tests -- forward declarations
+
+
+file_exists = (path) ->
+  f = io.open path, 'r'
+  if f
+    f\close!
+    true
+  else
+    false
+
+
+read_file = (path) ->
+  f = assert io.open path, 'r'
+  contents = f\read '*a'
+  f\close!
+  contents
+
+
+write_file = (path, contents) ->
+  f = assert io.open path, 'w'
+  f\write contents
+  f\close!
+
+
+included_tests_from_toml = (path) ->
+  included = {}
+  local uuid, last_uuid
+  line_no = 0
+
+  for line in io.lines(path)
+    line_no += 1
+    for uuid in line\gmatch('%[([%x%-]+)%]')
+      last_uuid = uuid
+      included[uuid] = true
+
+    if line\match('^include%s*=%s*false')
+      included[last_uuid] = nil
+
+  included
+
+
+export indent, quote -- mark as global so spec_generators can see them
+
+indent = (text, level) -> string.rep('  ', level) .. text
+
+quote = (str) ->
+  if str\find "'"
+    "\"#{str\gsub '"', '\\"'}\""
+  else
+    "'#{str}'"
+
+
+test_cmd = 'it'
+
+process = (node, level=0) ->
+  if node.cases
+    output = {}
+
+    if node.description
+      table.insert output, indent("describe #{quote node.description}, ->", level)
+    else
+      table.insert output, indent("describe '#{exercise_name}', ->", level)
+
+      if spec_generator.test_helpers
+        table.insert output, spec_generator.test_helpers
+
+    cases = {}
+    for case in *node.cases
+      if not case.uuid or included_tests[case.uuid]
+        table.insert cases, process(case, level + 1)
+
+    table.insert output, table.concat(cases, '\n')
+
+    return table.concat output, '\n'
+
+  else -- no "cases" member
+    test = "#{test_cmd} #{quote node.description}, ->\n#{spec_generator.generate_test(node, level + 1)}\n"
+    test_cmd = 'pending'
+    return indent test, level
+
+-- ----------------------------------------------------------
+-- "main"
+-- ----------------------------------------------------------
+exercise_name = arg[1]
+snake_name = exercise_name\gsub("-", "_")
+
+-- to differentiate from the lua rock "say" required by busted.
+if snake_name == 'say'
+  snake_name = './say'
+
+exercise_directory = 'exercises/practice/' .. exercise_name
+
+canonical_data_url = "https://raw.githubusercontent.com/exercism/problem-specifications/main/exercises/#{exercise_name}/canonical-data.json"
+canonical_data_path = "canonical-data/#{exercise_name}.json"
+
+assert os.execute('mkdir -p "$(dirname "' .. canonical_data_path .. '")"')
+assert os.execute('curl "' .. canonical_data_url .. '" -s -o "' .. canonical_data_path .. '"')
+
+canonical_data = json.decode read_file canonical_data_path
+
+tests_toml_path = exercise_directory .. '/.meta/tests.toml'
+included_tests = included_tests_from_toml tests_toml_path
+
+package.moonpath = "#{exercise_directory}/.meta/?.moon;#{package.moonpath}"
+spec_generator = require 'spec_generator'
+
+local spec
+if spec_generator.module_name
+  spec = "#{spec_generator.module_name} = require '#{snake_name}'"
+elseif spec_generator.module_imports
+  spec = "import #{table.concat spec_generator.module_imports, ', '} from require '#{snake_name}'"
+else
+  error 'spec_generator is missing both "module_name" and "module_imports"'
+
+spec ..= "\n\n" .. process(canonical_data)
+
+spec_path = exercise_directory .. '/' .. snake_name .. '_spec.moon'
+write_file spec_path, spec
+
+print "Created #{spec_path}"
diff --git a/bin/test-all b/bin/test-all
new file mode 100755
index 0000000..f31d8c8
--- /dev/null
+++ b/bin/test-all
@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+start=$SECONDS
+
+unset CDPATH
+
+script_dir=$(realpath "$(dirname "$0")")
+
+cd "${script_dir}/../exercises/practice" || exit 4
+result=0
+count=0
+
+for exercise in *; do
+    [[ -d $exercise ]] || continue
+
+    "$script_dir"/test-one "$exercise" || (( ++result ))
+    (( ++count ))
+done
+
+echo
+echo "$count exercises tested in $(( SECONDS - start )) seconds."
+
+exit $result
diff --git a/bin/test-one b/bin/test-one
new file mode 100755
index 0000000..e8ec430
--- /dev/null
+++ b/bin/test-one
@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+#
+# shellcheck disable=SC2164
+
+if [[ -z $1 ]]; then
+    echo "Usage: $0 exercise-slug" >&2
+    exit 2
+fi
+
+unset CDPATH
+
+cd "$(realpath "$(dirname "$0")/..")"
+
+exercise=$1
+shift
+exercise_dir=$(realpath "exercises/practice/$exercise")
+
+if [[ ! -d $exercise_dir ]]; then
+    echo "No such exercise: $exercise" >&2
+    exit 3
+fi
+
+test_dir=$( mktemp -d )
+trap 'rm -rf "$test_dir"' EXIT
+
+cd "$test_dir" || exit 4
+(cd "$exercise_dir"; tar cf - .) | tar xf -
+
+echo >&2
+echo "Testing $exercise..." >&2
+
+IFS=$'\t' read -r solution tests example < <(
+    jq -r '.files | [.solution[0], .test[0], .example[0]] | @tsv' .meta/config.json
+)
+
+mv "$example" "$solution"
+perl -i -pe 's/^\s+\Kpending\b/it/' "$tests"
+
+busted --verbose "$@"
diff --git a/config.json b/config.json
index 145c83f..bed5c08 100644
--- a/config.json
+++ b/config.json
@@ -8,23 +8,53 @@
     "representer": false,
     "analyzer": false
   },
-  "blurb": "TODO: add blurb",
+  "blurb": "MoonScript is a dynamic scripting language that compiles into Lua. It gives you the power of one of the fastest scripting languages combined with a rich set of features.",
   "version": 3,
   "online_editor": {
     "indent_style": "space",
-    "indent_size": 4
+    "indent_size": 2,
+    "highlightjs_language": "moonscript"
   },
   "files": {
-    "solution": [],
-    "test": [],
-    "example": [],
-    "exemplar": []
+    "solution": [
+      "%{snake_slug}.moon"
+    ],
+    "test": [
+      "%{snake_slug}_spec.moon"
+    ],
+    "example": [
+      ".meta/example.moon"
+    ],
+    "exemplar": [
+      ".meta/exemplar.moon"
+    ]
   },
   "exercises": {
-    "concept": [],
-    "practice": []
+    "practice": [
+      {
+        "slug": "hello-world",
+        "name": "Hello World",
+        "uuid": "09b9866a-3f90-461b-8baf-70d9f0c02322",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 1
+      }
+    ]
   },
-  "concepts": [],
-  "key_features": [],
-  "tags": []
+  "tags": [
+    "execution_mode/interpreted",
+    "paradigm/imperative",
+    "paradigm/object_oriented",
+    "paradigm/procedural",
+    "platform/linux",
+    "platform/mac",
+    "platform/windows",
+    "runtime/language_specific",
+    "typing/dynamic",
+    "used_for/backends",
+    "used_for/cross_platform_development",
+    "used_for/embedded_systems",
+    "used_for/games",
+    "used_for/scripts"
+  ]
 }
diff --git a/exercises/practice/hello-world/.busted b/exercises/practice/hello-world/.busted
new file mode 100644
index 0000000..86b84e7
--- /dev/null
+++ b/exercises/practice/hello-world/.busted
@@ -0,0 +1,5 @@
+return {
+  default = {
+    ROOT = { '.' }
+  }
+}
diff --git a/exercises/practice/hello-world/.docs/instructions.md b/exercises/practice/hello-world/.docs/instructions.md
new file mode 100644
index 0000000..c9570e4
--- /dev/null
+++ b/exercises/practice/hello-world/.docs/instructions.md
@@ -0,0 +1,16 @@
+# Instructions
+
+The classical introductory exercise.
+Just say "Hello, World!".
+
+["Hello, World!"][hello-world] is the traditional first program for beginning programming in a new language or environment.
+
+The objectives are simple:
+
+- Modify the provided code so that it produces the string "Hello, World!".
+- Run the test suite and make sure that it succeeds.
+- Submit your solution and check it at the website.
+
+If everything goes well, you will be ready to fetch your first real exercise.
+
+[hello-world]: https://en.wikipedia.org/wiki/%22Hello,_world!%22_program
diff --git a/exercises/practice/hello-world/.meta/config.json b/exercises/practice/hello-world/.meta/config.json
new file mode 100644
index 0000000..cfd6bb6
--- /dev/null
+++ b/exercises/practice/hello-world/.meta/config.json
@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "glennj"
+  ],
+  "files": {
+    "solution": [
+      "hello_world.moon"
+    ],
+    "test": [
+      "hello_world_spec.moon"
+    ],
+    "example": [
+      ".meta/example.moon"
+    ]
+  },
+  "blurb": "Exercism's classic introductory exercise. Just say \"Hello, World!\".",
+  "source": "This is an exercise to introduce users to using Exercism",
+  "source_url": "https://en.wikipedia.org/wiki/%22Hello,_world!%22_program"
+}
diff --git a/exercises/practice/hello-world/.meta/example.moon b/exercises/practice/hello-world/.meta/example.moon
new file mode 100644
index 0000000..e8adead
--- /dev/null
+++ b/exercises/practice/hello-world/.meta/example.moon
@@ -0,0 +1,7 @@
+require "moonscript"
+
+hello = ->
+  "Hello, World!"
+
+{ :hello }
+
diff --git a/exercises/practice/hello-world/.meta/tests.toml b/exercises/practice/hello-world/.meta/tests.toml
new file mode 100644
index 0000000..73466d6
--- /dev/null
+++ b/exercises/practice/hello-world/.meta/tests.toml
@@ -0,0 +1,13 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[af9ffe10-dc13-42d8-a742-e7bdafac449d]
+description = "Say Hi!"
diff --git a/exercises/practice/hello-world/hello_world.moon b/exercises/practice/hello-world/hello_world.moon
new file mode 100644
index 0000000..1952403
--- /dev/null
+++ b/exercises/practice/hello-world/hello_world.moon
@@ -0,0 +1,6 @@
+require "moonscript"
+
+hello = ->
+  'Goodbye, Mars!'
+
+{ :hello }
diff --git a/exercises/practice/hello-world/hello_world_spec.moon b/exercises/practice/hello-world/hello_world_spec.moon
new file mode 100644
index 0000000..92ba366
--- /dev/null
+++ b/exercises/practice/hello-world/hello_world_spec.moon
@@ -0,0 +1,10 @@
+-- Require the hello-world module
+hello_world = require 'hello_world'
+
+-- Define a module named hello-world. This module should return a single
+-- function named hello that takes no arguments and returns a string.
+
+describe 'hello-world', ->
+  it 'says hello world', ->
+    result = hello_world.hello!
+    assert.are.equal 'Hello, World!', result