test: cover CLI workspace resolver, date picker, saturating version

Add regression tests for the bugs found in this smoke test:

- resolve_workspace: by-name, by-UUID, unknown-identifier, current-fallback,
  actionable no-workspace message.
- DateTimePicker: selected-day highlight must be month-scoped; committing
  after navigating months uses the selected month, not the viewed one.
- create_task: version is saturating_add on u64::MAX (doesn't panic/wrap).

Also fixes the three pre-existing clippy warnings (WorkspaceMode now uses
#[derive(Default)] + #[default], repository test drops unused binding,
sync test uses struct-update syntax instead of field-reassign-default).

apps/tauri/src/lib/components/DateTimePicker.test.ts

@@ -0,0 +1,74 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen, cleanup } from "@testing-library/svelte";
+import userEvent from "@testing-library/user-event";
+import DateTimePicker from "./DateTimePicker.svelte";
+
+beforeEach(() => {
+  cleanup();
+});
+
+describe("DateTimePicker — selected highlight", () => {
+  it("only marks the selected day in the month/year that was actually picked", async () => {
+    const user = userEvent.setup();
+    // Pick a date in the current month so the component opens on it.
+    const now = new Date();
+    const existing = new Date(now.getFullYear(), now.getMonth(), 15, 0, 0, 0).toISOString();
+
+    render(DateTimePicker, {
+      value: existing,
+      has_time: false,
+      onchange: vi.fn(),
+      onclose: vi.fn(),
+    });
+
+    // The "15" button for the current month should be rendered with the
+    // selected styling (bg-primary).
+    const day15 = screen.getByRole("button", { name: "15" });
+    expect(day15.className).toMatch(/bg-primary/);
+
+    // Navigate one month forward. The same "15" cell must NOT be marked as
+    // selected, because the user hasn't picked a day in that month yet.
+    const nextMonthBtn = screen.getAllByRole("button").find((b) =>
+      b.querySelector("svg path[d*='M7.21 14.77']"),
+    ) as HTMLElement;
+    await user.click(nextMonthBtn);
+
+    const nextMonth15 = screen.getByRole("button", { name: "15" });
+    expect(nextMonth15.className).not.toMatch(/bg-primary/);
+  });
+
+  it("commits based on the last-selected month, not the currently-viewed month", async () => {
+    const user = userEvent.setup();
+    const onchange = vi.fn();
+    const onclose = vi.fn();
+
+    // Start with April 10 selected (use a fixed month/year so the test is stable).
+    const existing = new Date(2026, 3, 10, 0, 0, 0).toISOString();
+    render(DateTimePicker, {
+      value: existing,
+      has_time: false,
+      onchange,
+      onclose,
+    });
+
+    // Pick the 20th while viewing April.
+    await user.click(screen.getByRole("button", { name: "20" }));
+
+    // Flip to May.
+    const nextMonthBtn = screen.getAllByRole("button").find((b) =>
+      b.querySelector("svg path[d*='M7.21 14.77']"),
+    ) as HTMLElement;
+    await user.click(nextMonthBtn);
+
+    // Hit Done.
+    await user.click(screen.getByRole("button", { name: "Done" }));
+
+    expect(onchange).toHaveBeenCalled();
+    const committed = new Date(onchange.mock.calls[0][0] as string);
+    // April == month 3 (0-indexed). We navigated to May without reselecting,
+    // so the committed date must still be April 20.
+    expect(committed.getMonth()).toBe(3);
+    expect(committed.getDate()).toBe(20);
+    expect(committed.getFullYear()).toBe(2026);
+  });
+});

crates/onyx-cli/src/commands/mod.rs

@@ -53,3 +53,60 @@ pub fn get_repository(workspace_identifier: Option<String>) -> Result<(TaskRepos
 
     Ok((repo, name))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn make_config_with(ws: &[(&str, &str)]) -> (AppConfig, Vec<String>) {
+        let mut config = AppConfig::new();
+        let ids: Vec<String> = ws.iter()
+            .map(|(name, path)| config.add_workspace(WorkspaceConfig::new(name.to_string(), PathBuf::from(path))))
+            .collect();
+        (config, ids)
+    }
+
+    #[test]
+    fn resolve_by_name() {
+        let (config, _ids) = make_config_with(&[("dev", "/tmp/dev"), ("home", "/tmp/home")]);
+        let (id, ws) = resolve_workspace(&config, Some("dev")).unwrap();
+        assert_eq!(ws.name, "dev");
+        assert!(config.workspaces.contains_key(&id));
+    }
+
+    #[test]
+    fn resolve_by_uuid() {
+        let (config, ids) = make_config_with(&[("dev", "/tmp/dev")]);
+        let target = ids[0].clone();
+        let (id, ws) = resolve_workspace(&config, Some(&target)).unwrap();
+        assert_eq!(id, target);
+        assert_eq!(ws.name, "dev");
+    }
+
+    #[test]
+    fn resolve_unknown_identifier_errors() {
+        let (config, _ids) = make_config_with(&[("dev", "/tmp/dev")]);
+        let err = resolve_workspace(&config, Some("ghost")).unwrap_err();
+        assert!(err.to_string().contains("Workspace 'ghost' not found"));
+    }
+
+    #[test]
+    fn resolve_falls_back_to_current() {
+        let (mut config, ids) = make_config_with(&[("a", "/tmp/a"), ("b", "/tmp/b")]);
+        config.set_current_workspace(ids[1].clone()).unwrap();
+        let (id, ws) = resolve_workspace(&config, None).unwrap();
+        assert_eq!(id, ids[1]);
+        assert_eq!(ws.name, "b");
+    }
+
+    #[test]
+    fn resolve_no_current_gives_actionable_message() {
+        let config = AppConfig::new();
+        let err = resolve_workspace(&config, None).unwrap_err();
+        let msg = err.to_string();
+        // The message should point the user at the right sub-commands, not
+        // at the obsolete 'onyx init' suggestion.
+        assert!(msg.contains("workspace add") || msg.contains("workspace switch"),
+            "expected actionable message, got: {msg}");
+    }
+}

crates/onyx-core/src/config.rs

@@ -4,20 +4,15 @@ use serde::{Deserialize, Serialize};
 use uuid::Uuid;
 use crate::error::{Error, Result};
 
-#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Default)]
 #[serde(rename_all = "lowercase")]
 pub enum WorkspaceMode {
+    #[default]
     Local,
     Webdav,
     GoogleTasks,
 }
 
-impl Default for WorkspaceMode {
-    fn default() -> Self {
-        Self::Local
-    }
-}
-
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct WorkspaceConfig {
     pub name: String,

crates/onyx-core/src/repository.rs

@@ -157,7 +157,7 @@ mod tests {
 
         // Create a task
         let task = Task::new("Test Task".to_string());
-        let created_task = repo.create_task(list.id, task).unwrap();
+        let _ = repo.create_task(list.id, task).unwrap();
 
         // List tasks
         let tasks = repo.list_tasks(list.id).unwrap();
@@ -165,6 +165,20 @@ mod tests {
         assert_eq!(tasks[0].title, "Test Task");
     }
 
+    #[test]
+    fn test_create_task_saturates_version_at_max() {
+        let temp_dir = TempDir::new().unwrap();
+        let mut repo = TaskRepository::init(temp_dir.path().to_path_buf()).unwrap();
+        let list = repo.create_list("L".to_string()).unwrap();
+
+        // Simulate a task that is already at u64::MAX. A plain `+=` would
+        // overflow — saturating_add must clamp.
+        let mut task = Task::new("max".to_string());
+        task.version = u64::MAX;
+        let created = repo.create_task(list.id, task).unwrap();
+        assert_eq!(created.version, u64::MAX);
+    }
+
     #[test]
     fn test_update_task() {
         let temp_dir = TempDir::new().unwrap();

crates/onyx-core/src/sync.rs

@@ -1137,8 +1137,7 @@ mod tests {
     #[test]
     fn test_sync_state_save_load_roundtrip() {
         let temp_dir = TempDir::new().unwrap();
-        let mut state = SyncState::default();
+        let mut state = SyncState { last_sync: Some(Utc::now()), ..Default::default() };
-        state.last_sync = Some(Utc::now());
         state.record_file("test.md", "abc123", Some("2026-01-01T00:00:00Z"), 42);
 
         state.save(temp_dir.path()).unwrap();