diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..9510ba0
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,23 @@
+name: test
+
+on:
+  push:
+    branches:
+      - master
+      - main
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: erlef/setup-beam@v1
+        with:
+          otp-version: "26.0.2"
+          gleam-version: "0.33.0"
+          rebar3-version: "3"
+          # elixir-version: "1.15.4"
+      - run: gleam deps download
+      - run: gleam test
+      - run: gleam format --check src test
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..170cca9
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+*.beam
+*.ez
+build
+erl_crash.dump
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..5db44d9
--- /dev/null
+++ b/README.md
@@ -0,0 +1,22 @@
+# justin
+
+[![Package Version](https://img.shields.io/hexpm/v/justin)](https://hex.pm/packages/justin)
+[![Hex Docs](https://img.shields.io/badge/hex-docs-ffaff3)](https://hexdocs.pm/justin/)
+
+## Quick start
+
+```sh
+gleam run   # Run the project
+gleam test  # Run the tests
+gleam shell # Run an Erlang shell
+```
+
+## Installation
+
+If available on Hex this package can be added to your Gleam project:
+
+```sh
+gleam add justin
+```
+
+and its documentation can be found at <https://hexdocs.pm/justin>.
diff --git a/gleam.toml b/gleam.toml
new file mode 100644
index 0000000..7ee4a80
--- /dev/null
+++ b/gleam.toml
@@ -0,0 +1,16 @@
+name = "justin"
+version = "1.0.0"
+
+# Fill out these fields if you intend to generate HTML documentation or publish
+# your project to the Hex package manager.
+#
+# description = ""
+# licences = ["Apache-2.0"]
+# repository = { type = "github", user = "username", repo = "project" }
+# links = [{ title = "Website", href = "https://gleam.run" }]
+
+[dependencies]
+gleam_stdlib = "~> 0.32"
+
+[dev-dependencies]
+gleeunit = "~> 1.0"
diff --git a/manifest.toml b/manifest.toml
new file mode 100644
index 0000000..e1aa028
--- /dev/null
+++ b/manifest.toml
@@ -0,0 +1,11 @@
+# This file was generated by Gleam
+# You typically do not need to edit this file
+
+packages = [
+  { name = "gleam_stdlib", version = "0.34.0", build_tools = ["gleam"], requirements = [], otp_app = "gleam_stdlib", source = "hex", outer_checksum = "1FB8454D2991E9B4C0C804544D8A9AD0F6184725E20D63C3155F0AEB4230B016" },
+  { name = "gleeunit", version = "1.0.2", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleeunit", source = "hex", outer_checksum = "D364C87AFEB26BDB4FB8A5ABDE67D635DC9FA52D6AB68416044C35B096C6882D" },
+]
+
+[requirements]
+gleam_stdlib = { version = "~> 0.32" }
+gleeunit = { version = "~> 1.0" }
diff --git a/src/justin.gleam b/src/justin.gleam
new file mode 100644
index 0000000..5391b57
--- /dev/null
+++ b/src/justin.gleam
@@ -0,0 +1,101 @@
+import gleam/string
+import gleam/io
+import gleam/list
+
+// TODO: document
+pub fn snake_case(text: String) -> String {
+  text
+  |> split_words
+  |> string.join("_")
+  |> string.lowercase
+}
+
+// TODO: document
+pub fn camel_case(text: String) -> String {
+  text
+  |> split_words
+  |> list.index_map(fn(word, i) {
+    case i {
+      0 -> string.lowercase(word)
+      _ -> string.capitalise(word)
+    }
+  })
+  |> string.concat
+}
+
+// TODO: document
+pub fn pascal_case(text: String) -> String {
+  text
+  |> split_words
+  |> list.map(string.capitalise)
+  |> string.concat
+}
+
+// TODO: document
+pub fn kebab_case(text: String) -> String {
+  text
+  |> split_words
+  |> string.join("-")
+  |> string.lowercase
+}
+
+// TODO: document
+pub fn sentence_case(text: String) -> String {
+  text
+  |> split_words
+  |> string.join(" ")
+  |> string.capitalise
+}
+
+fn split_words(text: String) -> List(String) {
+  text
+  |> string.to_graphemes
+  |> split(False, "", [])
+}
+
+fn split(
+  in: List(String),
+  up: Bool,
+  word: String,
+  words: List(String),
+) -> List(String) {
+  case in {
+    [] if word == "" -> list.reverse(words)
+    [] -> list.reverse(add(words, word))
+
+    ["\n", ..in]
+    | ["\t", ..in]
+    | ["!", ..in]
+    | ["?", ..in]
+    | ["#", ..in]
+    | [".", ..in]
+    | ["-", ..in]
+    | ["_", ..in]
+    | [" ", ..in] -> split(in, False, "", add(words, word))
+
+    [g, ..in] -> {
+      io.println(string.inspect(#(g, is_upper(g))))
+      case is_upper(g) {
+        // Lowercase, not a new word
+        False -> split(in, False, word <> g, words)
+
+        // Uppercase and inside an uppercase word, not a new word
+        True if up -> split(in, up, word <> g, words)
+
+        // Uppercase otherwise, a new word
+        True -> split(in, True, g, add(words, word))
+      }
+    }
+  }
+}
+
+fn add(words: List(String), word: String) -> List(String) {
+  case word {
+    "" -> words
+    _ -> [word, ..words]
+  }
+}
+
+fn is_upper(g: String) -> Bool {
+  string.lowercase(g) != g
+}
diff --git a/test/justin_test.gleam b/test/justin_test.gleam
new file mode 100644
index 0000000..6571756
--- /dev/null
+++ b/test/justin_test.gleam
@@ -0,0 +1,121 @@
+import gleeunit
+import gleam/list
+import justin
+
+pub fn main() {
+  gleeunit.main()
+}
+
+const snake_cases = [
+  #("", ""),
+  #("snake case", "snake_case"),
+  #("snakeCase", "snake_case"),
+  #("Snake-Case", "snake_case"),
+  #("Snake_Case", "snake_case"),
+  #("SnakeCase", "snake_case"),
+  #("Snake.Case", "snake_case"),
+  #("SNAKE_CASE", "snake_case"),
+  #("--snake-case--", "snake_case"),
+  #("snake#case", "snake_case"),
+  #("snake?!case", "snake_case"),
+  #("snake\tcase", "snake_case"),
+  #("snake\ncase", "snake_case"),
+  #("λambdaΛambda", "λambda_λambda"),
+]
+
+const camel_cases = [
+  #("", ""),
+  #("snake case", "snakeCase"),
+  #("snakeCase", "snakeCase"),
+  #("Snake-Case", "snakeCase"),
+  #("Snake_Case", "snakeCase"),
+  #("SnakeCase", "snakeCase"),
+  #("Snake.Case", "snakeCase"),
+  #("SNAKE_CASE", "snakeCase"),
+  #("--snake-case--", "snakeCase"),
+  #("snake#case", "snakeCase"),
+  #("snake?!case", "snakeCase"),
+  #("snake\tcase", "snakeCase"),
+  #("snake\ncase", "snakeCase"),
+  #("λambda_λambda", "λambdaΛambda"),
+]
+
+const pascal_cases = [
+  #("", ""),
+  #("snake case", "SnakeCase"),
+  #("snakeCase", "SnakeCase"),
+  #("Snake-Case", "SnakeCase"),
+  #("Snake_Case", "SnakeCase"),
+  #("SnakeCase", "SnakeCase"),
+  #("Snake.Case", "SnakeCase"),
+  #("SNAKE_CASE", "SnakeCase"),
+  #("--snake-case--", "SnakeCase"),
+  #("snake#case", "SnakeCase"),
+  #("snake?!case", "SnakeCase"),
+  #("snake\tcase", "SnakeCase"),
+  #("snake\ncase", "SnakeCase"),
+  #("λambda_λambda", "ΛambdaΛambda"),
+]
+
+const kebab_cases = [
+  #("", ""),
+  #("snake case", "snake-case"),
+  #("snakeCase", "snake-case"),
+  #("Snake-Case", "snake-case"),
+  #("Snake_Case", "snake-case"),
+  #("SnakeCase", "snake-case"),
+  #("Snake.Case", "snake-case"),
+  #("SNAKE_CASE", "snake-case"),
+  #("--snake-case--", "snake-case"),
+  #("snake#case", "snake-case"),
+  #("snake?!case", "snake-case"),
+  #("snake\tcase", "snake-case"),
+  #("snake\ncase", "snake-case"),
+  #("λambda_λambda", "λambda-λambda"),
+]
+
+const sentence_cases = [
+  #("", ""),
+  #("snake case", "Snake case"),
+  #("snakeCase", "Snake case"),
+  #("Snake-Case", "Snake case"),
+  #("Snake_Case", "Snake case"),
+  #("SnakeCase", "Snake case"),
+  #("Snake.Case", "Snake case"),
+  #("SNAKE_CASE", "Snake case"),
+  #("--snake-case--", "Snake case"),
+  #("snake#case", "Snake case"),
+  #("snake?!case", "Snake case"),
+  #("snake\tcase", "Snake case"),
+  #("snake\ncase", "Snake case"),
+  #("λambda_λambda", "Λambda λambda"),
+]
+
+fn run_cases(cases: List(#(String, String)), function: fn(String) -> String) {
+  use #(in, out) <- list.each(cases)
+  let real = function(in)
+  case real == out {
+    True -> Nil
+    False -> panic as { in <> " should be " <> out <> ", got " <> real }
+  }
+}
+
+pub fn snake_test() {
+  run_cases(snake_cases, justin.snake_case)
+}
+
+pub fn camel_test() {
+  run_cases(camel_cases, justin.camel_case)
+}
+
+pub fn pascal_test() {
+  run_cases(pascal_cases, justin.pascal_case)
+}
+
+pub fn kebab_test() {
+  run_cases(kebab_cases, justin.kebab_case)
+}
+
+pub fn sentence_test() {
+  run_cases(sentence_cases, justin.sentence_case)
+}