Add -Werror, fix unused import warnings

- Add -Werror to ghc-options for both library and test suite
- Remove unused Data.Maybe import from Internal.hs
- Remove unused Data.Int and Data.Text imports from test files

.gitea/workflows/build.yaml

@@ -0,0 +1,41 @@
+name: Build and Test
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  build-and-test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          submodules: true
+
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y -qq libsqlite3-dev
+
+      - name: Install Stack
+        run: |
+          curl -sSL https://get.haskellstack.org/ | sh
+
+      - name: Cache Stack artifacts
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.stack
+            .stack-work
+          key: stack-${{ runner.os }}-${{ hashFiles('stack.yaml', 'orville-sqlite.cabal') }}
+          restore-keys: |
+            stack-${{ runner.os }}-
+
+      - name: Build
+        run: stack build --pedantic
+
+      - name: Test
+        run: stack test

README.md

@@ -1,61 +1,154 @@
 # orville-sqlite
 
-This library is intended to be a SQLite Haskell API similar in spirit to https://github.com/flipstone/orville/
+A type-safe SQLite API for Haskell, modeled after the [Flipstone Orville](https://github.com/flipstone/orville/) PostgreSQL library.
 
-The goal of this library is to provide a type safe approach to mapping Haskell types to SQLite data. We aim for type-safe queries and migrations.
+Maps Haskell data types to SQLite tables with compile-time schema guarantees.
 
-The Flipstone orville library is robust and deep. This library aspires to the same but realizes it's unlikely to get there anytime soon.
+## Status — MVP
 
-## Goal
+The MVP provides the core pipeline: define columns and record marshallers, auto-migrate schemas, and execute basic CRUD queries.
 
-This library intends to provide a similar API for describing the database schema and executing queries as the Flipstone Orville library.
-
-We will not port the PostgreSQL implementation directly but instead target a similar API.
-
-The APIs that concern us the most are:
-
-- Orville.PostgreSQL.Marshall.SqlMarshaller
-- Orville.PostgreSQL.AutoMigration as AutoMigration
-- Orville.PostgreSQL.Execution
-
-and even for those, we only what's strictly necessary to define a way to take a Haskell data type like
+## Usage
 
 ```haskell
+{-# LANGUAGE DataKinds #-}
 
-data Person =
+import Orville.SQLite
+
+data Person = Person
+  { personId :: Int64
+  , firstName :: Text
+  , lastName :: Text
+  , age :: Int64
+  }
+  deriving (Show, Eq)
+
+-- Column definitions (type-safe, parameterized by nullability)
+personIdField :: FieldDefinition 'NotNull Int64
+personIdField = integerField "id"
+
+firstNameField :: FieldDefinition 'NotNull Text
+firstNameField = textField "first_name"
+
+lastNameField :: FieldDefinition 'NotNull Text
+lastNameField = textField "last_name"
+
+ageField :: FieldDefinition 'NotNull Int64
+ageField = integerField "age"
+
+-- SqlMarshaller: maps the record to/from SQL columns
+personMarshaller :: SqlMarshaller Person Person
+personMarshaller =
   Person
-    { firstName :: Text
-    , lastName :: Text
-    , age :: Int
-    }
+    <$> marshallReadOnlyField personIdField  -- auto-increment PK
+    <*> marshallField firstName firstNameField
+    <*> marshallField lastName lastNameField
+    <*> marshallField age ageField
+
+-- TableDefinition ties a table name, primary key, and marshaller together
+personTable :: TableDefinition Int64 Person Person
+personTable =
+  mkTableDefinition "person" (primaryKey personId personIdField) personMarshaller
+
+main :: IO ()
+main = do
+  db <- openConnection "people.db"
+  withConnection db $ do
+    -- Auto-migrate: creates the table if it doesn't exist
+    autoMigrateSchema defaultOptions [schemaTable personTable []]
+
+    -- Insert
+    insertEntity personTable (Person 0 "Alice" "Smith" 30)
+    insertEntity personTable (Person 0 "Bob"   "Jones" 25)
+
+    -- Query by primary key
+    mAlice <- findEntity personTable 1
+    -- mAlice = Just (Person 1 "Alice" "Smith" 30)
+
+    -- Find all
+    all <- findAll personTable
+    -- all = [Person 1 "Alice" "Smith" 30, Person 2 "Bob" "Jones" 25]
+
+    -- Update
+    updateEntity personTable (Person 1 "Alice" "Jones" 31)
+
+    -- Delete
+    deleteEntity personTable 2
+
+    pure ()
+  closeConnection db
 ```
 
-and map it to a table of schema
+The above creates this table:
 
 ```sql
-CREATE TABLE person (
-    first_name VARCHAR(100) NOT NULL,
-    last_name  VARCHAR(100) NOT NULL,
-    age        INT
+CREATE TABLE IF NOT EXISTS person (
+  age INTEGER NOT NULL,
+  last_name TEXT NOT NULL,
+  first_name TEXT NOT NULL,
+  id INTEGER PRIMARY KEY
 );
 ```
 
-and then give us an API for marshalling that Haskell type to that table definition
+## Modules
 
-then using that marshaller we should have APIs that can;
+| Module | Purpose |
+|--------|---------|
+| `Orville.SQLite` | Top-level re-exports |
+| `Orville.SQLite.Monad` | `OrvilleM` reader monad and connection management |
+| `Orville.SQLite.SqlType` | Type encoding/decoding for SQLite storage classes |
+| `Orville.SQLite.FieldDefinition` | GADT column definitions with `NotNull`/`Nullable` |
+| `Orville.SQLite.SqlMarshaller` | GADT record-to-table mapping (applicative syntax) |
+| `Orville.SQLite.TableDefinition` | `PrimaryKey` and `mkTableDefinition` |
+| `Orville.SQLite.AutoMigration` | Schema introspection via `PRAGMA table_info`, DDL generation |
+| `Orville.SQLite.Execution` | `insertEntity`, `findEntity`, `findAll`, `updateEntity`, `deleteEntity` |
 
-- create the table if it does not exist
-- alter the table to match the schema if the table does exist but its columns don't match
-- query the table and retrieve Person values
-- insert Person values into the table
-- update the table from Person values.
+## Feature Coverage
 
-## Development environment
+### Included (MVP)
 
-The development environment should be entirely inside of Docker - no local
-tools should be installed on the machine directly. use the `hs` wrapper script
-to execute Haskell tooling inside of Docker.
+- `FieldDefinition` with `NotNull`/`Nullable` type parameters
+- `SqlMarshaller` GADT with `marshallField`, `marshallReadOnlyField`, `marshallMaybe`
+- `TableDefinition` with single-column primary keys
+- `AutoMigration`: create tables, add nullable columns, drop columns (explicit opt-in), dry-run
+- `Execution`: insert, find-by-PK, find-all, update, delete
+- In-memory databases (`:memory:`) and file-based databases
 
-## Base SQLite library
+### Not yet implemented
 
-Our base library for interacting with SQLite should be direct-sqlite - https://github.com/IreneKnapp/direct-sqlite
+- Foreign keys and composite primary keys
+- Table indexes
+- Plans (N+1 query prevention via `Plan`)
+- Batch operations
+- Upsert (`upsertEntity`)
+- `findEntitiesBy` (filtering on non-PK columns)
+- `updateFields` (partial update)
+- Raw SQL execution (`executeAndDecode`)
+- Nested record marshalling and `prefixMarshaller`
+- `AnnotatedSqlMarshaller`
+- `SyntheticField`
+- Connection pooling
+
+## Development
+
+All tooling runs inside Docker via the `./hs` wrapper. No local Haskell installation needed.
+
+```bash
+./hs stack build       # build
+./hs stack test        # run tests (53 tests)
+./hs stack ghci        # REPL
+./hs fourmolu -i src/  # format
+```
+
+Or use the convenience scripts:
+
+```bash
+./scripts/build         # build with pedantic
+./scripts/test          # run tests
+```
+
+### Dependencies
+
+- GHC 9.10.3
+- [direct-sqlite](https://github.com/IreneKnapp/direct-sqlite) — low-level FFI binding to SQLite
+- `text`, `bytestring`, `mtl`

orville-sqlite.cabal

@@ -19,7 +19,9 @@ library
       Orville.SQLite.AutoMigration
       Orville.SQLite.Execution
       Orville.SQLite.FieldDefinition
+      Orville.SQLite.Internal
       Orville.SQLite.Monad
+      Orville.SQLite.Raw
       Orville.SQLite.RawSql
       Orville.SQLite.SqlMarshaller
       Orville.SQLite.SqlType
@@ -32,16 +34,26 @@ library
     , text
     , bytestring
   default-language: Haskell2010
-  ghc-options: -Wall
+  ghc-options: -Wall -Werror
 
 test-suite spec
   type: exitcode-stdio-1.0
   main-is: Main.hs
+  other-modules:
+      Test.Setup
+      Test.AutoMigration
+      Test.EntityOperations
+      Test.FieldDefinition
+      Test.Raw
+      Test.SqlMarshaller
   hs-source-dirs: test
   build-depends:
       base >=4.17 && <5
+    , bytestring
+    , direct-sqlite
     , mtl
     , orville-sqlite
     , hspec
     , text
   default-language: Haskell2010
+  ghc-options: -Wall -Werror

scripts/build

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
+
+cd "$PROJECT_DIR"
+./hs stack build "$@"

scripts/test

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
+
+cd "$PROJECT_DIR"
+./hs stack test "$@"

src/Orville/SQLite.hs

@@ -13,12 +13,15 @@ module Orville.SQLite
   , module Orville.SQLite.AutoMigration
     -- * Execution
   , module Orville.SQLite.Execution
+    -- * Raw
+  , module Orville.SQLite.Raw
   ) where
 
 import Orville.SQLite.AutoMigration
 import Orville.SQLite.Execution
 import Orville.SQLite.FieldDefinition
 import Orville.SQLite.Monad
+import Orville.SQLite.Raw
 import Orville.SQLite.SqlMarshaller
 import Orville.SQLite.SqlType
 import Orville.SQLite.TableDefinition

src/Orville/SQLite/Execution.hs

@@ -15,8 +15,8 @@ import Control.Monad.Reader (ask)
 import Data.List (intercalate)
 import qualified Data.Text as T
 import qualified Database.SQLite3 as SQLite3
-import Database.SQLite3.Direct (columnCount)
 import Orville.SQLite.FieldDefinition (fieldColumnName, fieldToSqlValue)
+import Orville.SQLite.Internal (getRowData)
 import Orville.SQLite.Monad (OrvilleM)
 import Orville.SQLite.SqlMarshaller (
     marshallerDecodeRow,
@@ -148,22 +148,4 @@ deleteEntity tableDef key = do
         _ <- SQLite3.step stmt
         SQLite3.finalize stmt
 
-getRowData ::
-    SQLite3.Statement ->
-    [String] ->
-    IO [(String, SQLite3.SQLData)]
-getRowData stmt cols = do
-    colCount <- columnCount stmt
-    let count :: Int = fromIntegral colCount
-        indexes = take count [0 :: SQLite3.ColumnIndex ..]
-    mapM
-        ( \i -> do
-            let idx :: Int = fromIntegral i
-                colName =
-                    if idx < length cols
-                        then cols !! idx
-                        else ""
-            sqlVal <- SQLite3.column stmt i
-            pure (colName, sqlVal)
-        )
-        indexes
+

src/Orville/SQLite/Internal.hs

@@ -0,0 +1,28 @@
+{-# LANGUAGE ScopedTypeVariables #-}
+
+module Orville.SQLite.Internal (
+    getRowData,
+) where
+
+import Control.Monad (forM)
+import qualified Data.Text as T
+import qualified Database.SQLite3 as SQLite3
+import Database.SQLite3.Direct (columnCount)
+
+getRowData ::
+    SQLite3.Statement ->
+    [String] ->
+    IO [(String, SQLite3.SQLData)]
+getRowData stmt cols = do
+    colCount <- columnCount stmt
+    let count :: Int = fromIntegral colCount
+        indexes = take count [0 :: SQLite3.ColumnIndex ..]
+    forM indexes $ \i -> do
+        let idx :: Int = fromIntegral i
+            -- Try column name from statement metadata first, then fall back to provided names, then empty
+        mName <- SQLite3.columnName stmt i
+        let colName = case mName of
+                Just n | not (T.null n) -> T.unpack n
+                _ -> if idx < length cols then cols !! idx else ""
+        sqlVal <- SQLite3.column stmt i
+        pure (colName, sqlVal)

src/Orville/SQLite/Raw.hs

@@ -0,0 +1,71 @@
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE OverloadedStrings #-}
+
+module Orville.SQLite.Raw (
+    execute,
+    executeWith,
+    query_,
+    queryWith,
+) where
+
+import Control.Monad.IO.Class (liftIO)
+import Control.Monad.Reader (ask)
+import qualified Data.Text as T
+import qualified Database.SQLite3 as SQLite3
+
+import Orville.SQLite.Internal (getRowData)
+import Orville.SQLite.Monad (OrvilleM)
+
+-- | Execute a raw SQL statement with no parameters.
+execute :: T.Text -> OrvilleM ()
+execute sql = do
+    db <- ask
+    liftIO $ do
+        stmt <- SQLite3.prepare db sql
+        _ <- SQLite3.step stmt
+        SQLite3.finalize stmt
+
+-- | Execute a raw SQL statement with bound parameters.
+executeWith :: T.Text -> [SQLite3.SQLData] -> OrvilleM ()
+executeWith sql params = do
+    db <- ask
+    liftIO $ do
+        stmt <- SQLite3.prepare db sql
+        SQLite3.bind stmt params
+        _ <- SQLite3.step stmt
+        SQLite3.finalize stmt
+
+-- | Execute a raw SQL query with no parameters and collect all rows.
+query_ :: T.Text -> OrvilleM [[(String, SQLite3.SQLData)]]
+query_ sql = do
+    db <- ask
+    liftIO $ do
+        stmt <- SQLite3.prepare db sql
+        let loop acc = do
+                stepResult <- SQLite3.step stmt
+                case stepResult of
+                    SQLite3.Done -> do
+                        SQLite3.finalize stmt
+                        pure (reverse acc)
+                    SQLite3.Row -> do
+                        rowData <- getRowData stmt []
+                        loop (rowData : acc)
+        loop []
+
+-- | Execute a raw SQL query with bound parameters and collect all rows.
+queryWith :: T.Text -> [SQLite3.SQLData] -> OrvilleM [[(String, SQLite3.SQLData)]]
+queryWith sql params = do
+    db <- ask
+    liftIO $ do
+        stmt <- SQLite3.prepare db sql
+        SQLite3.bind stmt params
+        let loop acc = do
+                stepResult <- SQLite3.step stmt
+                case stepResult of
+                    SQLite3.Done -> do
+                        SQLite3.finalize stmt
+                        pure (reverse acc)
+                    SQLite3.Row -> do
+                        rowData <- getRowData stmt []
+                        loop (rowData : acc)
+        loop []

test/Main.hs

@@ -1,92 +1,19 @@
-{-# LANGUAGE DataKinds #-}
 {-# LANGUAGE OverloadedStrings #-}
 
 module Main where
 
-import Control.Monad.IO.Class (liftIO)
-import Data.Int (Int64)
-import Data.Text (Text)
-import Orville.SQLite
 import Test.Hspec
 
-data Person = Person
-    { personId :: Int64
-    , firstName :: Text
-    , lastName :: Text
-    , age :: Int64
-    }
-    deriving (Show, Eq)
-
-personIdField :: FieldDefinition 'NotNull Int64
-personIdField = integerField "id"
-
-firstNameField :: FieldDefinition 'NotNull Text
-firstNameField = textField "first_name"
-
-lastNameField :: FieldDefinition 'NotNull Text
-lastNameField = textField "last_name"
-
-ageField :: FieldDefinition 'NotNull Int64
-ageField = integerField "age"
-
-personMarshaller :: SqlMarshaller Person Person
-personMarshaller =
-    Person
-        <$> marshallReadOnlyField personIdField
-        <*> marshallField firstName firstNameField
-        <*> marshallField lastName lastNameField
-        <*> marshallField age ageField
-
-personTable :: TableDefinition Int64 Person Person
-personTable =
-    mkTableDefinition "person" (primaryKey personId personIdField) personMarshaller
+import qualified Test.AutoMigration as AutoMigration
+import qualified Test.EntityOperations as EntityOperations
+import qualified Test.FieldDefinition as FieldDefinition
+import qualified Test.Raw as Raw
+import qualified Test.SqlMarshaller as SqlMarshaller
 
 main :: IO ()
 main = hspec $ do
-    describe "Orville.SQLite" $ do
-        it "creates a table and inserts a row" $ do
-            db <- openConnection ":memory:"
-            withConnection db $ do
-                autoMigrateSchema defaultOptions [schemaTable personTable []]
-                insertEntity personTable (Person 0 "Alice" "Smith" 30)
-                mAlice <- findEntity personTable 1
-                liftIO $ mAlice `shouldBe` Just (Person 1 "Alice" "Smith" 30)
-            closeConnection db
-
-        it "finds all rows" $ do
-            db <- openConnection ":memory:"
-            withConnection db $ do
-                autoMigrateSchema defaultOptions [schemaTable personTable []]
-                insertEntity personTable (Person 0 "Alice" "Smith" 30)
-                insertEntity personTable (Person 0 "Bob" "Jones" 25)
-                results <- findAll personTable
-                liftIO $ length results `shouldBe` 2
-            closeConnection db
-
-        it "updates a row" $ do
-            db <- openConnection ":memory:"
-            withConnection db $ do
-                autoMigrateSchema defaultOptions [schemaTable personTable []]
-                insertEntity personTable (Person 0 "Alice" "Smith" 30)
-                updateEntity personTable (Person 1 "Alice" "Jones" 31)
-                mAlice <- findEntity personTable 1
-                liftIO $ mAlice `shouldBe` Just (Person 1 "Alice" "Jones" 31)
-            closeConnection db
-
-        it "deletes a row" $ do
-            db <- openConnection ":memory:"
-            withConnection db $ do
-                autoMigrateSchema defaultOptions [schemaTable personTable []]
-                insertEntity personTable (Person 0 "Alice" "Smith" 30)
-                deleteEntity personTable 1
-                mAlice <- findEntity personTable 1
-                liftIO $ mAlice `shouldBe` Nothing
-            closeConnection db
-
-        it "returns Nothing for missing row" $ do
-            db <- openConnection ":memory:"
-            withConnection db $ do
-                autoMigrateSchema defaultOptions [schemaTable personTable []]
-                mAlice <- findEntity personTable 999
-                liftIO $ mAlice `shouldBe` Nothing
-            closeConnection db
+    describe "FieldDefinition" FieldDefinition.fieldDefinitionTests
+    describe "SqlMarshaller" SqlMarshaller.sqlMarshallerTests
+    describe "EntityOperations" EntityOperations.entityOperationsTests
+    describe "AutoMigration" AutoMigration.autoMigrationTests
+    describe "Raw" Raw.rawTests

test/Test/AutoMigration.hs

@@ -0,0 +1,93 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+
+module Test.AutoMigration where
+
+import Control.Exception (SomeException, try)
+import Control.Monad.IO.Class (liftIO)
+import Test.Hspec
+
+import Orville.SQLite
+import Test.Setup
+
+autoMigrationTests :: Spec
+autoMigrationTests = do
+    describe "autoMigrateSchema" $ do
+        it "creates a table that does not exist" $ do
+            db <- openConnection ":memory:"
+            withConnection db $ do
+                autoMigrateSchema defaultOptions [schemaTable personTable []]
+                pure ()
+            closeConnection db
+
+        it "is idempotent -- running twice does not error" $ do
+            db <- openConnection ":memory:"
+            withConnection db $ do
+                autoMigrateSchema defaultOptions [schemaTable personTable []]
+                autoMigrateSchema defaultOptions [schemaTable personTable []]
+                pure ()
+            closeConnection db
+
+        it "creates multiple tables at once" $ do
+            db <- openConnection ":memory:"
+            withConnection db $ do
+                autoMigrateSchema
+                    defaultOptions
+                    [ schemaTable personTable []
+                    , schemaTable widgetTable []
+                    ]
+                pure ()
+            closeConnection db
+
+        it "adds a new nullable column via ALTER TABLE" $ do
+            db <- openConnection ":memory:"
+            withConnection db $ do
+                autoMigrateSchema defaultOptions [existingTableSchema]
+                insertEntity widgetTable (Widget 1 "Test")
+                autoMigrateSchema defaultOptions [schemaTable widgetTable []]
+                mWidget <- findEntity widgetTable 1
+                liftIO $ mWidget `shouldBe` Just (Widget 1 "Test")
+            closeConnection db
+
+        it "attempting to use old marshaller after column drop fails" $ do
+            db <- openConnection ":memory:"
+            result <- liftIO $ try $ withConnection db $ do
+                autoMigrateSchema defaultOptions [schemaTable personTable []]
+                insertEntity personTable (Person 0 "Alice" "Smith" 30)
+                autoMigrateSchema defaultOptions [schemaTable personTable ["age"]]
+                -- This will fail because the marshaller still references the age column
+                findEntity personTable 1
+            closeConnection db
+            liftIO $
+                result `shouldSatisfy` \case
+                    Left (_ :: SomeException) -> True
+                    Right _ -> False
+
+        it "dry run does not create tables" $ do
+            db <- openConnection ":memory:"
+            withConnection db $ do
+                autoMigrateSchema
+                    defaultOptions{runSchemaChanges = False}
+                    [schemaTable personTable []]
+                -- Migration is skipped; table should not exist
+                result <-
+                    liftIO $
+                        try $
+                            withConnection db $
+                                insertEntity personTable (Person 0 "Alice" "Smith" 30)
+                liftIO $
+                    result `shouldSatisfy` \case
+                        Left (_ :: SomeException) -> True
+                        Right _ -> False
+            closeConnection db
+
+-- | Schema that only has widget_id (no label), representing an older version.
+existingTableSchema :: SchemaItem
+existingTableSchema =
+    let
+        marshaller = Widget <$> marshallField widgetId widgetIdField <*> marshallReadOnlyField widgetLabelField
+        tableDef = mkTableDefinition "widget" (primaryKey widgetId widgetIdField) marshaller
+     in
+        schemaTable tableDef []

test/Test/EntityOperations.hs

@@ -0,0 +1,130 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE OverloadedStrings #-}
+
+module Test.EntityOperations where
+
+import Control.Monad.IO.Class (liftIO)
+import Test.Hspec
+
+import Orville.SQLite
+import Test.Setup
+
+entityOperationsTests :: Spec
+entityOperationsTests = do
+    describe "insertEntity" $ do
+        it "inserts a row and returns via findEntity" $ do
+            let p = Person 0 "Alice" "Smith" 30
+            mAlice <- withFreshDb personTable $ do
+                insertEntity personTable p
+                findEntity personTable 1
+            liftIO $ mAlice `shouldBe` Just (Person 1 "Alice" "Smith" 30)
+
+        it "assigns auto-increment ids sequentially" $ do
+            results <- withFreshDb personTable $ do
+                insertEntity personTable (Person 0 "A" "One" 20)
+                insertEntity personTable (Person 0 "B" "Two" 25)
+                insertEntity personTable (Person 0 "C" "Three" 30)
+                findAll personTable
+            liftIO $ map personId results `shouldBe` [1, 2, 3]
+
+        it "inserts an entity with explicit PK (non-auto-increment)" $ do
+            let w = Widget 42 "TestWidget"
+            mWidget <- withFreshDb widgetTable $ do
+                insertEntity widgetTable w
+                findEntity widgetTable 42
+            liftIO $ mWidget `shouldBe` Just w
+
+        it "inserts an entity with a nullable field set to Just" $ do
+            let t = Task 0 "Buy groceries" (Just 15)
+            mTask <- withFreshDb taskTable $ do
+                insertEntity taskTable t
+                findEntity taskTable 1
+            liftIO $ mTask `shouldBe` Just (Task 1 "Buy groceries" (Just 15))
+
+        it "inserts an entity with a nullable field set to Nothing" $ do
+            let t = Task 0 "No due date" Nothing
+            mTask <- withFreshDb taskTable $ do
+                insertEntity taskTable t
+                findEntity taskTable 1
+            liftIO $ mTask `shouldBe` Just (Task 1 "No due date" Nothing)
+
+    describe "findEntity" $ do
+        it "returns Nothing for a non-existent key" $ do
+            result <-
+                withFreshDb personTable $
+                    findEntity personTable 999
+            liftIO $ result `shouldBe` Nothing
+
+        it "returns Nothing on an empty table" $ do
+            result <-
+                withFreshDb personTable $
+                    findEntity personTable 1
+            liftIO $ result `shouldBe` Nothing
+
+    describe "findAll" $ do
+        it "returns all inserted rows" $ do
+            results <- withFreshDb personTable $ do
+                insertEntity personTable (Person 0 "Alice" "Smith" 30)
+                insertEntity personTable (Person 0 "Bob" "Jones" 25)
+                findAll personTable
+            liftIO $ length results `shouldBe` 2
+
+        it "returns empty list on empty table" $ do
+            results <-
+                withFreshDb personTable $
+                    findAll personTable
+            liftIO $ results `shouldBe` []
+
+        it "returns rows in insertion order" $ do
+            results <- withFreshDb personTable $ do
+                insertEntity personTable (Person 0 "First" "One" 10)
+                insertEntity personTable (Person 0 "Second" "Two" 20)
+                insertEntity personTable (Person 0 "Third" "Three" 30)
+                findAll personTable
+            liftIO $ map firstName results `shouldBe` ["First", "Second", "Third"]
+
+    describe "updateEntity" $ do
+        it "updates a row and returns via findEntity" $ do
+            result <- withFreshDb personTable $ do
+                insertEntity personTable (Person 0 "Alice" "Smith" 30)
+                updateEntity personTable (Person 1 "Alice" "Jones" 31)
+                findEntity personTable 1
+            liftIO $ result `shouldBe` Just (Person 1 "Alice" "Jones" 31)
+
+        it "updates a widget with explicit PK" $ do
+            result <- withFreshDb widgetTable $ do
+                insertEntity widgetTable (Widget 10 "OldLabel")
+                updateEntity widgetTable (Widget 10 "NewLabel")
+                findEntity widgetTable 10
+            liftIO $ result `shouldBe` Just (Widget 10 "NewLabel")
+
+        it "does not affect other rows" $ do
+            results <- withFreshDb personTable $ do
+                insertEntity personTable (Person 0 "Alice" "Smith" 30)
+                insertEntity personTable (Person 0 "Bob" "Jones" 25)
+                updateEntity personTable (Person 1 "Alice" "Updated" 99)
+                findAll personTable
+            liftIO $ map firstName results `shouldBe` ["Alice", "Bob"]
+
+    describe "deleteEntity" $ do
+        it "deletes a row" $ do
+            result <- withFreshDb personTable $ do
+                insertEntity personTable (Person 0 "Alice" "Smith" 30)
+                deleteEntity personTable 1
+                findEntity personTable 1
+            liftIO $ result `shouldBe` Nothing
+
+        it "does not delete other rows" $ do
+            results <- withFreshDb personTable $ do
+                insertEntity personTable (Person 0 "Alice" "Smith" 30)
+                insertEntity personTable (Person 0 "Bob" "Jones" 25)
+                deleteEntity personTable 1
+                findAll personTable
+            liftIO $ map firstName results `shouldBe` ["Bob"]
+
+        it "deleting non-existent key does nothing" $ do
+            results <- withFreshDb personTable $ do
+                insertEntity personTable (Person 0 "Alice" "Smith" 30)
+                deleteEntity personTable 999
+                findAll personTable
+            liftIO $ length results `shouldBe` 1

test/Test/FieldDefinition.hs

@@ -0,0 +1,95 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TypeApplications #-}
+
+module Test.FieldDefinition where
+
+import qualified Data.ByteString as BS
+import Data.Int (Int64)
+import qualified Data.Text as T
+import Test.Hspec
+
+import qualified Database.SQLite3 as SQLite3
+import Orville.SQLite
+
+fieldDefinitionTests :: Spec
+fieldDefinitionTests = do
+    describe "integerField" $ do
+        it "roundtrips encode/decode" $ do
+            let fd = integerField "count"
+            let val = 42 :: Int64
+            fieldFromSqlValue (fieldToSqlValue val fd) fd `shouldBe` Right val
+
+        it "encodes to SQLInteger" $ do
+            let fd = integerField "count"
+            fieldToSqlValue 99 fd `shouldBe` SQLite3.SQLInteger 99
+
+        it "decodes from SQLInteger" $ do
+            let fd = integerField "count"
+            fieldFromSqlValue (SQLite3.SQLInteger 99) fd `shouldBe` Right 99
+
+    describe "textField" $ do
+        it "roundtrips encode/decode" $ do
+            let fd = textField "name"
+            let val = "Hello" :: T.Text
+            fieldFromSqlValue (fieldToSqlValue val fd) fd `shouldBe` Right val
+
+        it "encodes to SQLText" $ do
+            let fd = textField "name"
+            fieldToSqlValue "test" fd `shouldBe` SQLite3.SQLText "test"
+
+        it "decodes from SQLText" $ do
+            let fd = textField "name"
+            fieldFromSqlValue (SQLite3.SQLText "decoded") fd `shouldBe` Right ("decoded" :: T.Text)
+
+    describe "realField" $ do
+        it "roundtrips encode/decode" $ do
+            let fd = realField "price"
+            let val = 3.14 :: Double
+            fieldFromSqlValue (fieldToSqlValue val fd) fd `shouldBe` Right val
+
+        it "encodes to SQLFloat" $ do
+            let fd = realField "price"
+            fieldToSqlValue 2.718 fd `shouldBe` SQLite3.SQLFloat 2.718
+
+    describe "blobField" $ do
+        it "roundtrips encode/decode" $ do
+            let fd = blobField "data"
+            let val = "binary\0stuff" :: BS.ByteString
+            fieldFromSqlValue (fieldToSqlValue val fd) fd `shouldBe` Right val
+
+    describe "nullableField" $ do
+        it "is marked as nullable" $ do
+            let fd = nullableField (integerField "opt")
+            fieldIsNullable fd `shouldBe` True
+
+        it "retains the column name" $ do
+            let fd = nullableField (textField "notes")
+            fieldColumnName fd `shouldBe` "notes"
+
+    describe "convertField" $ do
+        it "converts between types" $ do
+            let fd = integerField "count"
+            let converted = convertField show (read @Int64) fd :: FieldDefinition 'NotNull String
+            fieldFromSqlValue (SQLite3.SQLInteger 123) converted `shouldBe` Right "123"
+
+    describe "fieldColumnName" $ do
+        it "returns the column name for non-null field" $ do
+            fieldColumnName (integerField "my_col") `shouldBe` "my_col"
+
+        it "returns the column name for nullable field" $ do
+            fieldColumnName (nullableField (textField "opt_col")) `shouldBe` "opt_col"
+
+    describe "fieldSqlTypeName" $ do
+        it "returns INTEGER for integerField" $ do
+            fieldSqlTypeName (integerField "x") `shouldBe` "INTEGER"
+
+        it "returns TEXT for textField" $ do
+            fieldSqlTypeName (textField "x") `shouldBe` "TEXT"
+
+        it "returns REAL for realField" $ do
+            fieldSqlTypeName (realField "x") `shouldBe` "REAL"
+
+        it "returns BLOB for blobField" $ do
+            fieldSqlTypeName (blobField "x") `shouldBe` "BLOB"

test/Test/Raw.hs

@@ -0,0 +1,48 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module Test.Raw where
+
+import qualified Database.SQLite3 as SQLite3
+import Test.Hspec
+
+import Orville.SQLite
+
+rawTests :: Spec
+rawTests = do
+    describe "execute" $ do
+        it "runs a CREATE TABLE and INSERT statement" $ do
+            db <- openConnection ":memory:"
+            runOrvilleM db $ execute "CREATE TABLE raw_test (id INTEGER, name TEXT)"
+            runOrvilleM db $ execute "INSERT INTO raw_test VALUES (1, 'hello')"
+            rows <- runOrvilleM db $ query_ "SELECT * FROM raw_test"
+            length rows `shouldBe` 1
+            closeConnection db
+
+    describe "executeWith" $ do
+        it "runs parameterized INSERT" $ do
+            db <- openConnection ":memory:"
+            runOrvilleM db $ execute "CREATE TABLE raw_test2 (id INTEGER, name TEXT)"
+            runOrvilleM db $ executeWith "INSERT INTO raw_test2 VALUES (?, ?)" [SQLite3.SQLInteger 42, SQLite3.SQLText "world"]
+            rows <- runOrvilleM db $ query_ "SELECT * FROM raw_test2"
+            length rows `shouldBe` 1
+            closeConnection db
+
+    describe "query_" $ do
+        it "returns rows from a SELECT" $ do
+            db <- openConnection ":memory:"
+            runOrvilleM db $ execute "CREATE TABLE raw_test3 (a INTEGER)"
+            runOrvilleM db $ execute "INSERT INTO raw_test3 VALUES (1)"
+            runOrvilleM db $ execute "INSERT INTO raw_test3 VALUES (2)"
+            rows <- runOrvilleM db $ query_ "SELECT * FROM raw_test3 ORDER BY a"
+            length rows `shouldBe` 2
+            closeConnection db
+
+    describe "queryWith" $ do
+        it "returns rows matching parameters" $ do
+            db <- openConnection ":memory:"
+            runOrvilleM db $ execute "CREATE TABLE raw_test4 (name TEXT)"
+            runOrvilleM db $ executeWith "INSERT INTO raw_test4 VALUES (?)" [SQLite3.SQLText "alpha"]
+            runOrvilleM db $ executeWith "INSERT INTO raw_test4 VALUES (?)" [SQLite3.SQLText "beta"]
+            rows <- runOrvilleM db $ queryWith "SELECT * FROM raw_test4 WHERE name = ?" [SQLite3.SQLText "beta"]
+            length rows `shouldBe` 1
+            closeConnection db

test/Test/Setup.hs

@@ -0,0 +1,106 @@
+{-# LANGUAGE DataKinds #-}
+
+module Test.Setup where
+
+import Data.Int (Int64)
+import Data.Text (Text)
+
+import Orville.SQLite
+
+{- | A simple entity for testing, with an auto-increment primary key.
+The PK (personId) is read-only — SQLite populates it via INTEGER PRIMARY KEY.
+-}
+data Person = Person
+    { personId :: Int64
+    , firstName :: Text
+    , lastName :: Text
+    , age :: Int64
+    }
+    deriving (Show, Eq)
+
+personIdField :: FieldDefinition 'NotNull Int64
+personIdField = integerField "id"
+
+firstNameField :: FieldDefinition 'NotNull Text
+firstNameField = textField "first_name"
+
+lastNameField :: FieldDefinition 'NotNull Text
+lastNameField = textField "last_name"
+
+ageField :: FieldDefinition 'NotNull Int64
+ageField = integerField "age"
+
+personMarshaller :: SqlMarshaller Person Person
+personMarshaller =
+    Person
+        <$> marshallReadOnlyField personIdField
+        <*> marshallField firstName firstNameField
+        <*> marshallField lastName lastNameField
+        <*> marshallField age ageField
+
+personTable :: TableDefinition Int64 Person Person
+personTable =
+    mkTableDefinition "person" (primaryKey personId personIdField) personMarshaller
+
+-- | An entity where the PK is part of the write entity (not auto-increment).
+data Widget = Widget
+    { widgetId :: Int64
+    , widgetLabel :: Text
+    }
+    deriving (Show, Eq)
+
+widgetIdField :: FieldDefinition 'NotNull Int64
+widgetIdField = integerField "widget_id"
+
+widgetLabelField :: FieldDefinition 'NotNull Text
+widgetLabelField = textField "label"
+
+widgetMarshaller :: SqlMarshaller Widget Widget
+widgetMarshaller =
+    Widget
+        <$> marshallField widgetId widgetIdField
+        <*> marshallField widgetLabel widgetLabelField
+
+widgetTable :: TableDefinition Int64 Widget Widget
+widgetTable =
+    mkTableDefinition "widget" (primaryKey widgetId widgetIdField) widgetMarshaller
+
+-- | An entity with a nullable field.
+data Task = Task
+    { taskId :: Int64
+    , taskDescription :: Text
+    , taskDueDay :: Maybe Int64
+    }
+    deriving (Show, Eq)
+
+taskIdField :: FieldDefinition 'NotNull Int64
+taskIdField = integerField "task_id"
+
+taskDescriptionField :: FieldDefinition 'NotNull Text
+taskDescriptionField = textField "description"
+
+taskDueDayField :: FieldDefinition 'Nullable Int64
+taskDueDayField = nullableField (integerField "due_day")
+
+taskMarshaller :: SqlMarshaller Task Task
+taskMarshaller =
+    Task
+        <$> marshallReadOnlyField taskIdField
+        <*> marshallField taskDescription taskDescriptionField
+        <*> marshallMaybe taskDueDay taskDueDayField
+
+taskTable :: TableDefinition Int64 Task Task
+taskTable =
+    mkTableDefinition "task" (primaryKey taskId taskIdField) taskMarshaller
+
+{- | Run an OrvilleM action against a fresh in-memory database,
+with the given table created via auto-migration.
+-}
+withFreshDb :: TableDefinition key w r -> OrvilleM a -> IO a
+withFreshDb tableDef action = do
+    db <- openConnection ":memory:"
+    result <- withConnection db $ do
+        autoMigrateSchema defaultOptions [schemaTable tableDef []]
+        action
+    closeConnection db
+    pure result

test/Test/SqlMarshaller.hs

@@ -0,0 +1,108 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE OverloadedStrings #-}
+
+module Test.SqlMarshaller where
+
+import qualified Data.Text as T
+import Test.Hspec
+
+import qualified Database.SQLite3 as SQLite3
+import Orville.SQLite
+import Test.Setup
+
+sqlMarshallerTests :: Spec
+sqlMarshallerTests = do
+    describe "marshallerFieldInfo" $ do
+        it "enumerates all fields including read-only" $ do
+            let info = marshallerFieldInfo personMarshaller
+            map fieldInfoName info `shouldBe` ["age", "last_name", "first_name", "id"]
+
+        it "reports correct types" $ do
+            let info = marshallerFieldInfo personMarshaller
+            let types = [(fieldInfoName i, fieldInfoType i) | i <- info]
+            lookup "id" types `shouldBe` Just "INTEGER"
+            lookup "first_name" types `shouldBe` Just "TEXT"
+            lookup "last_name" types `shouldBe` Just "TEXT"
+            lookup "age" types `shouldBe` Just "INTEGER"
+
+    describe "marshallerDerivedColumns" $ do
+        it "lists all column names" $ do
+            let cols = marshallerDerivedColumns personMarshaller
+            length cols `shouldBe` 4
+
+    describe "marshallerEncodeWrite" $ do
+        it "excludes read-only fields" $ do
+            let p = Person 0 "Alice" "Smith" 30
+            let pairs = marshallerEncodeWrite personMarshaller p
+            let names = map fst pairs
+            names `shouldNotContain` ["id"]
+
+        it "includes all write fields" $ do
+            let p = Person 0 "Alice" "Smith" 30
+            let pairs = marshallerEncodeWrite personMarshaller p
+            let names = map fst pairs
+            names `shouldBe` ["age", "last_name", "first_name"]
+
+        it "encodes correct values" $ do
+            let p = Person 0 "Alice" "Smith" 30
+            let pairs = marshallerEncodeWrite personMarshaller p
+            lookup "first_name" pairs `shouldBe` Just (SQLite3.SQLText "Alice")
+            lookup "last_name" pairs `shouldBe` Just (SQLite3.SQLText "Smith")
+            lookup "age" pairs `shouldBe` Just (SQLite3.SQLInteger 30)
+
+        it "encodes nullable field as SQLNull when Nothing" $ do
+            let t = Task 0 "No due" Nothing
+            let pairs = marshallerEncodeWrite taskMarshaller t
+            lookup "due_day" pairs `shouldBe` Just SQLite3.SQLNull
+
+        it "encodes nullable field as SQLInteger when Just" $ do
+            let t = Task 0 "Has due" (Just 10)
+            let pairs = marshallerEncodeWrite taskMarshaller t
+            lookup "due_day" pairs `shouldBe` Just (SQLite3.SQLInteger 10)
+
+    describe "marshallerDecodeRow" $ do
+        it "decodes a complete row" $ do
+            let row =
+                    [ ("id", SQLite3.SQLInteger 1)
+                    , ("first_name", SQLite3.SQLText "Alice")
+                    , ("last_name", SQLite3.SQLText "Smith")
+                    , ("age", SQLite3.SQLInteger 30)
+                    ]
+            marshallerDecodeRow personMarshaller row `shouldBe` Right (Person 1 "Alice" "Smith" 30)
+
+        it "reports missing column" $ do
+            let row =
+                    [ ("first_name", SQLite3.SQLText "Alice")
+                    , ("last_name", SQLite3.SQLText "Smith")
+                    , ("age", SQLite3.SQLInteger 30)
+                    ]
+            marshallerDecodeRow personMarshaller row `shouldSatisfy` \case
+                Left e -> "id" `T.isInfixOf` T.pack e
+                Right _ -> False
+
+    describe "marshallReadOnlyField" $ do
+        it "is included in decode but excluded from encode" $ do
+            let p = Person 0 "Alice" "Smith" 30
+            let pairs = marshallerEncodeWrite personMarshaller p
+            let colNames = marshallerDerivedColumns personMarshaller
+            colNames `shouldContain` ["id"] -- id appears in SELECT
+            map fst pairs `shouldNotContain` ["id"] -- id not in INSERT values
+    describe "marshallMaybe" $ do
+        it "decodes SQLNull as Nothing" $ do
+            let row =
+                    [ ("task_id", SQLite3.SQLInteger 1)
+                    , ("description", SQLite3.SQLText "Test")
+                    , ("due_day", SQLite3.SQLNull)
+                    ]
+            marshallerDecodeRow taskMarshaller row
+                `shouldBe` Right (Task 1 "Test" Nothing)
+
+        it "decodes SQLInteger as Just" $ do
+            let row =
+                    [ ("task_id", SQLite3.SQLInteger 1)
+                    , ("description", SQLite3.SQLText "Test")
+                    , ("due_day", SQLite3.SQLInteger 25)
+                    ]
+            marshallerDecodeRow taskMarshaller row
+                `shouldBe` Right (Task 1 "Test" (Just 25))