diff --git a/src-tauri/src/db/mod.rs b/src-tauri/src/db/mod.rs
index f261111..bf3a4bc 100644
--- a/src-tauri/src/db/mod.rs
+++ b/src-tauri/src/db/mod.rs
@@ -47,3 +47,95 @@ impl Database {
         Ok(())
     }
 }
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn open_in_memory() {
+        let db = Database::open(Path::new(":memory:"));
+        assert!(db.is_ok());
+    }
+
+    #[test]
+    fn migrate_creates_tables() {
+        let db = Database::open(Path::new(":memory:")).unwrap();
+        db.migrate().unwrap();
+
+        let conn = db.conn();
+        let tables: Vec<String> = conn
+            .prepare("SELECT name FROM sqlite_master WHERE type='table' ORDER BY name")
+            .unwrap()
+            .query_map([], |row| row.get(0))
+            .unwrap()
+            .collect::<Result<Vec<_>, _>>()
+            .unwrap();
+
+        assert!(tables.contains(&"connections".to_string()));
+        assert!(tables.contains(&"credentials".to_string()));
+        assert!(tables.contains(&"groups".to_string()));
+        assert!(tables.contains(&"host_keys".to_string()));
+        assert!(tables.contains(&"settings".to_string()));
+        assert!(tables.contains(&"themes".to_string()));
+        assert!(tables.contains(&"ssh_keys".to_string()));
+        assert!(tables.contains(&"connection_history".to_string()));
+    }
+
+    #[test]
+    fn migrate_is_idempotent() {
+        let db = Database::open(Path::new(":memory:")).unwrap();
+        db.migrate().unwrap();
+        db.migrate().unwrap(); // second run must not error
+    }
+
+    #[test]
+    fn foreign_keys_enabled() {
+        let db = Database::open(Path::new(":memory:")).unwrap();
+        let conn = db.conn();
+        let fk_enabled: i64 = conn
+            .query_row("PRAGMA foreign_keys", [], |row| row.get(0))
+            .unwrap();
+        assert_eq!(fk_enabled, 1);
+    }
+
+    #[test]
+    fn wal_mode_enabled() {
+        let db = Database::open(Path::new(":memory:")).unwrap();
+        // In-memory databases use "memory" journal mode, but WAL is set
+        // for file-backed DBs. Just verify the pragma doesn't error.
+        let conn = db.conn();
+        let mode: String = conn
+            .query_row("PRAGMA journal_mode", [], |row| row.get(0))
+            .unwrap();
+        // In-memory always reports "memory"; file-backed would report "wal".
+        assert!(!mode.is_empty());
+    }
+
+    #[test]
+    fn clone_shares_connection() {
+        let db = Database::open(Path::new(":memory:")).unwrap();
+        db.migrate().unwrap();
+
+        let db2 = db.clone();
+        // Write through one handle, read through the other.
+        db.conn()
+            .execute(
+                "INSERT INTO settings (key, value) VALUES ('test', 'yes')",
+                [],
+            )
+            .unwrap();
+
+        let val: String = db2
+            .conn()
+            .query_row("SELECT value FROM settings WHERE key = 'test'", [], |r| {
+                r.get(0)
+            })
+            .unwrap();
+        assert_eq!(val, "yes");
+    }
+}
diff --git a/src-tauri/src/rdp/input.rs b/src-tauri/src/rdp/input.rs
index 9dfcecd..4bc7b64 100644
--- a/src-tauri/src/rdp/input.rs
+++ b/src-tauri/src/rdp/input.rs
@@ -190,3 +190,121 @@ pub fn is_extended(scancode: u32) -> bool {
 pub fn scancode_value(scancode: u32) -> u8 {
     (scancode & 0xFF) as u8
 }
+
+// ── tests ─────────────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // ── scancode lookup ──────────────────────────────────────────────────────
+
+    #[test]
+    fn escape_key_maps_correctly() {
+        assert_eq!(js_key_to_scancode("Escape"), Some(0x0001));
+    }
+
+    #[test]
+    fn letter_keys_map_correctly() {
+        assert_eq!(js_key_to_scancode("KeyA"), Some(0x001E));
+        assert_eq!(js_key_to_scancode("KeyZ"), Some(0x002C));
+    }
+
+    #[test]
+    fn function_keys_map_correctly() {
+        assert_eq!(js_key_to_scancode("F1"), Some(0x003B));
+        assert_eq!(js_key_to_scancode("F12"), Some(0x0058));
+    }
+
+    #[test]
+    fn enter_key_maps_correctly() {
+        assert_eq!(js_key_to_scancode("Enter"), Some(0x001C));
+    }
+
+    #[test]
+    fn space_key_maps_correctly() {
+        assert_eq!(js_key_to_scancode("Space"), Some(0x0039));
+    }
+
+    #[test]
+    fn unknown_key_returns_none() {
+        assert_eq!(js_key_to_scancode("FakeKey"), None);
+        assert_eq!(js_key_to_scancode(""), None);
+    }
+
+    // ── extended key detection ───────────────────────────────────────────────
+
+    #[test]
+    fn non_extended_key_detected() {
+        assert!(!is_extended(0x001E)); // KeyA
+        assert!(!is_extended(0x0001)); // Escape
+    }
+
+    #[test]
+    fn extended_key_detected() {
+        assert!(is_extended(0xE038)); // AltRight
+        assert!(is_extended(0xE01D)); // ControlRight
+        assert!(is_extended(0xE048)); // ArrowUp
+    }
+
+    #[test]
+    fn arrow_keys_are_extended() {
+        let arrows = ["ArrowUp", "ArrowDown", "ArrowLeft", "ArrowRight"];
+        for key in arrows {
+            let sc = js_key_to_scancode(key).unwrap();
+            assert!(is_extended(sc), "{key} should be extended");
+        }
+    }
+
+    // ── scancode value extraction ────────────────────────────────────────────
+
+    #[test]
+    fn scancode_value_extracts_low_byte() {
+        assert_eq!(scancode_value(0x001E), 0x1E); // KeyA
+        assert_eq!(scancode_value(0xE038), 0x38); // AltRight — low byte only
+    }
+
+    #[test]
+    fn numpad_enter_is_extended() {
+        let sc = js_key_to_scancode("NumpadEnter").unwrap();
+        assert!(is_extended(sc));
+        assert_eq!(scancode_value(sc), 0x1C); // same low byte as regular Enter
+    }
+
+    // ── mouse flags ─────────────────────────────────────────────────────────
+
+    #[test]
+    fn mouse_flags_are_distinct_bits() {
+        let flags = [
+            mouse_flags::MOVE,
+            mouse_flags::BUTTON1,
+            mouse_flags::BUTTON2,
+            mouse_flags::BUTTON3,
+            mouse_flags::DOWN,
+            mouse_flags::WHEEL,
+            mouse_flags::WHEEL_NEG,
+            mouse_flags::HWHEEL,
+        ];
+        // Each flag should be a single power of 2 (or a known composite).
+        for &f in &flags {
+            assert!(f > 0, "flag should be nonzero");
+            assert!(f.count_ones() == 1, "flag {:#06x} should be a single bit", f);
+        }
+    }
+
+    #[test]
+    fn left_click_down_composable() {
+        let event = mouse_flags::BUTTON1 | mouse_flags::DOWN;
+        assert_eq!(event & mouse_flags::BUTTON1, mouse_flags::BUTTON1);
+        assert_eq!(event & mouse_flags::DOWN, mouse_flags::DOWN);
+    }
+
+    // ── coverage: every key in the map is reachable ─────────────────────────
+
+    #[test]
+    fn scancode_map_has_expected_size() {
+        // 13 Fn/Esc + 14 number row + 14 QWERTY + 13 home row + 12 bottom
+        // + 8 modifiers + 9 nav + 4 arrows + 17 numpad + 17 media + 3 intl = ~124
+        assert!(SCANCODE_MAP.len() >= 100, "map should have 100+ entries, got {}", SCANCODE_MAP.len());
+    }
+}
diff --git a/src-tauri/src/theme/mod.rs b/src-tauri/src/theme/mod.rs
index 614aae8..cc5fc58 100644
--- a/src-tauri/src/theme/mod.rs
+++ b/src-tauri/src/theme/mod.rs
@@ -337,3 +337,128 @@ fn map_theme_row(row: &rusqlite::Row<'_>) -> rusqlite::Result<Theme> {
         is_builtin: row.get(21)?,
     })
 }
+
+// ── tests ─────────────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::db::Database;
+
+    fn make_service() -> ThemeService {
+        let db = Database::open(std::path::Path::new(":memory:")).unwrap();
+        db.migrate().unwrap();
+        ThemeService::new(db)
+    }
+
+    #[test]
+    fn list_empty_before_seed() {
+        let svc = make_service();
+        assert!(svc.list().is_empty());
+    }
+
+    #[test]
+    fn seed_builtins_creates_seven_themes() {
+        let svc = make_service();
+        svc.seed_builtins();
+        let themes = svc.list();
+        assert_eq!(themes.len(), 7);
+    }
+
+    #[test]
+    fn seed_builtins_is_idempotent() {
+        let svc = make_service();
+        svc.seed_builtins();
+        svc.seed_builtins(); // second run must not duplicate
+        assert_eq!(svc.list().len(), 7);
+    }
+
+    #[test]
+    fn all_builtins_marked_as_builtin() {
+        let svc = make_service();
+        svc.seed_builtins();
+        for theme in svc.list() {
+            assert!(theme.is_builtin, "{} should be marked as builtin", theme.name);
+        }
+    }
+
+    #[test]
+    fn builtin_names_correct() {
+        let svc = make_service();
+        svc.seed_builtins();
+        let names: Vec<String> = svc.list().into_iter().map(|t| t.name).collect();
+        assert!(names.contains(&"Dracula".to_string()));
+        assert!(names.contains(&"Nord".to_string()));
+        assert!(names.contains(&"Monokai".to_string()));
+        assert!(names.contains(&"One Dark".to_string()));
+        assert!(names.contains(&"Solarized Dark".to_string()));
+        assert!(names.contains(&"Gruvbox Dark".to_string()));
+        assert!(names.contains(&"MobaXTerm Classic".to_string()));
+    }
+
+    #[test]
+    fn get_by_name_returns_theme() {
+        let svc = make_service();
+        svc.seed_builtins();
+        let theme = svc.get_by_name("Dracula");
+        assert!(theme.is_some());
+        let t = theme.unwrap();
+        assert_eq!(t.name, "Dracula");
+        assert_eq!(t.background, "#282a36");
+        assert_eq!(t.foreground, "#f8f8f2");
+    }
+
+    #[test]
+    fn get_by_name_missing_returns_none() {
+        let svc = make_service();
+        svc.seed_builtins();
+        assert!(svc.get_by_name("Nonexistent Theme").is_none());
+    }
+
+    #[test]
+    fn get_by_name_is_case_sensitive() {
+        let svc = make_service();
+        svc.seed_builtins();
+        assert!(svc.get_by_name("dracula").is_none()); // lowercase should not match
+    }
+
+    #[test]
+    fn all_themes_have_valid_hex_colors() {
+        let svc = make_service();
+        svc.seed_builtins();
+        for theme in svc.list() {
+            let colors = [
+                &theme.foreground, &theme.background, &theme.cursor,
+                &theme.black, &theme.red, &theme.green, &theme.yellow,
+                &theme.blue, &theme.magenta, &theme.cyan, &theme.white,
+                &theme.bright_black, &theme.bright_red, &theme.bright_green,
+                &theme.bright_yellow, &theme.bright_blue, &theme.bright_magenta,
+                &theme.bright_cyan, &theme.bright_white,
+            ];
+            for color in colors {
+                assert!(
+                    color.starts_with('#') && color.len() == 7,
+                    "Theme '{}' has invalid color: '{}'",
+                    theme.name,
+                    color
+                );
+            }
+        }
+    }
+
+    #[test]
+    fn list_ordered_builtin_first_then_name() {
+        let svc = make_service();
+        svc.seed_builtins();
+        let themes = svc.list();
+        // All are builtin, so should be ordered by name (case-insensitive)
+        for w in themes.windows(2) {
+            assert!(
+                w[0].name.to_lowercase() <= w[1].name.to_lowercase(),
+                "'{}' should come before '{}'",
+                w[0].name,
+                w[1].name
+            );
+        }
+    }
+}