test: add migration tests

tests/migrations.rs

@@ -0,0 +1,62 @@
+use sqlx::migrate::Migrator;
+use sqlx::sqlite::SqlitePoolOptions;
+use sqlx::SqlitePool;
+
+static MIGRATOR: Migrator = sqlx::migrate!("./migrations");
+
+async fn mem_pool() -> SqlitePool {
+    // NOTE: max_connections(1) is required because each :memory: connection
+    // creates a separate database
+    SqlitePoolOptions::new()
+        .max_connections(1)
+        .connect("sqlite::memory:")
+        .await
+        .expect("cannot open in-memory db")
+}
+
+async fn user_tables(pool: &SqlitePool) -> Vec<String> {
+    sqlx::query_scalar::<_, String>(
+        "SELECT name FROM sqlite_master
+         WHERE type = 'table'
+           AND name NOT LIKE '_sqlx%'
+           AND name NOT LIKE 'sqlite_%'
+         ORDER BY name",
+    )
+    .fetch_all(pool)
+    .await
+    .expect("cannot query sqlite_master")
+}
+
+#[tokio::test]
+async fn migrations_up() {
+    let pool = mem_pool().await;
+    MIGRATOR.run(&pool).await.expect("migrations failed");
+
+    let tables = user_tables(&pool).await;
+    assert!(tables.contains(&"todos".to_string()));
+    assert!(tables.contains(&"todo_tags".to_string()));
+}
+
+#[tokio::test]
+async fn migrations_down() {
+    let pool = mem_pool().await;
+    MIGRATOR.run(&pool).await.expect("run failed");
+    MIGRATOR.undo(&pool, 0).await.expect("undo failed");
+
+    let tables = user_tables(&pool).await;
+    assert!(tables.is_empty(), "tables should be gone after revert: {tables:?}");
+}
+
+#[tokio::test]
+async fn migrations_round_trip() {
+    let pool = mem_pool().await;
+
+    MIGRATOR.run(&pool).await.expect("first run failed");
+    let tables_before = user_tables(&pool).await;
+
+    MIGRATOR.undo(&pool, 0).await.expect("undo failed");
+    MIGRATOR.run(&pool).await.expect("second run failed");
+    let tables_after = user_tables(&pool).await;
+
+    assert_eq!(tables_before, tables_after);
+}