Ability to mock behaviours for tests

src/cache.rs

@@ -4,8 +4,6 @@ use std::path::PathBuf;
 use std::path::Path;
 use std::error::Error;
 use std::collections::HashMap;
-use std::collections::HashSet;
-use std::hash::Hash;
 use std::sync::{Arc, Mutex};
 use std::ffi::OsStr;
 
@@ -19,6 +17,9 @@ use crate::calendar::cached_calendar::CachedCalendar;
 use crate::calendar::CalendarId;
 use crate::calendar::SupportedComponents;
 
+#[cfg(feature = "local_calendar_mocks_remote_calendars")]
+use crate::mock_behaviour::MockBehaviour;
+
 const MAIN_FILE: &str = "data.json";
 
 /// A CalDAV source that stores its item in a local folder
@@ -27,8 +28,9 @@ pub struct Cache {
     backing_folder: PathBuf,
     data: CachedData,
 
+    /// In tests, we may add forced errors to this object
     #[cfg(feature = "local_calendar_mocks_remote_calendars")]
-    is_mocking_remote_source: bool,
+    mock_behaviour: Option<Arc<Mutex<MockBehaviour>>>,
 }
 
 #[derive(Default, Debug, Serialize, Deserialize)]
@@ -40,8 +42,8 @@ struct CachedData {
 impl Cache {
     /// Activate the "mocking remote source" features (i.e. tell its children calendars that they are mocked remote calendars)
     #[cfg(feature = "local_calendar_mocks_remote_calendars")]
-    pub fn set_is_mocking_remote_source(&mut self) {
-        self.is_mocking_remote_source = true;
+    pub fn set_mock_behaviour(&mut self, mock_behaviour: Option<Arc<Mutex<MockBehaviour>>>) {
+        self.mock_behaviour = mock_behaviour;
     }
 
 
@@ -91,7 +93,7 @@ impl Cache {
             data,
 
             #[cfg(feature = "local_calendar_mocks_remote_calendars")]
-            is_mocking_remote_source: false,
+            mock_behaviour: None,
         })
     }
 
@@ -107,7 +109,7 @@ impl Cache {
             data: CachedData::default(),
 
             #[cfg(feature = "local_calendar_mocks_remote_calendars")]
-            is_mocking_remote_source: false,
+            mock_behaviour: None,
         }
     }
 
@@ -169,6 +171,9 @@ impl Cache {
 #[async_trait]
 impl CalDavSource<CachedCalendar> for Cache {
     async fn get_calendars(&self) -> Result<HashMap<CalendarId, Arc<Mutex<CachedCalendar>>>, Box<dyn Error>> {
+        #[cfg(feature = "local_calendar_mocks_remote_calendars")]
+        self.mock_behaviour.as_ref().map_or(Ok(()), |b| b.lock().unwrap().can_get_calendars())?;
+
         Ok(self.data.calendars.iter()
             .map(|(id, cal)| (id.clone(), cal.clone()))
             .collect()
@@ -181,13 +186,16 @@ impl CalDavSource<CachedCalendar> for Cache {
 
     async fn create_calendar(&mut self, id: CalendarId, name: String, supported_components: SupportedComponents) -> Result<Arc<Mutex<CachedCalendar>>, Box<dyn Error>> {
         log::debug!("Inserting local calendar {}", id);
+        #[cfg(feature = "local_calendar_mocks_remote_calendars")]
+        self.mock_behaviour.as_ref().map_or(Ok(()), |b| b.lock().unwrap().can_create_calendar())?;
+
         let new_calendar = CachedCalendar::new(name, id.clone(), supported_components);
         let arc = Arc::new(Mutex::new(new_calendar));
 
         #[cfg(feature = "local_calendar_mocks_remote_calendars")]
-        if self.is_mocking_remote_source {
-            arc.lock().unwrap().set_is_mocking_remote_calendar();
-        }
+        if let Some(behaviour) = &self.mock_behaviour {
+            arc.lock().unwrap().set_mock_behaviour(Some(Arc::clone(behaviour)));
+        };
 
         match self.data.calendars.insert(id, arc.clone()) {
             Some(_) => Err("Attempt to insert calendar failed: there is alredy such a calendar.".into()),

src/calendar/cached_calendar.rs

@@ -10,6 +10,11 @@ use crate::calendar::{CalendarId, SupportedComponents};
 use crate::Item;
 use crate::item::ItemId;
 
+#[cfg(feature = "local_calendar_mocks_remote_calendars")]
+use std::sync::{Arc, Mutex};
+#[cfg(feature = "local_calendar_mocks_remote_calendars")]
+use crate::mock_behaviour::MockBehaviour;
+
 
 /// A calendar used by the [`cache`](crate::cache) module
 #[derive(Clone, Debug, Serialize, Deserialize)]
@@ -18,7 +23,8 @@ pub struct CachedCalendar {
     id: CalendarId,
     supported_components: SupportedComponents,
     #[cfg(feature = "local_calendar_mocks_remote_calendars")]
-    is_mocking_remote_calendar: bool,
+    #[serde(skip)]
+    mock_behaviour: Option<Arc<Mutex<MockBehaviour>>>,
 
     items: HashMap<ItemId, Item>,
 }
@@ -26,8 +32,8 @@ pub struct CachedCalendar {
 impl CachedCalendar {
     /// Activate the "mocking remote calendar" feature (i.e. ignore sync statuses, since this is what an actual CalDAV sever would do)
     #[cfg(feature = "local_calendar_mocks_remote_calendars")]
-    pub fn set_is_mocking_remote_calendar(&mut self) {
-        self.is_mocking_remote_calendar = true;
+    pub fn set_mock_behaviour(&mut self, mock_behaviour: Option<Arc<Mutex<MockBehaviour>>>) {
+        self.mock_behaviour = mock_behaviour;
     }
 
     /// Add an item
@@ -107,7 +113,10 @@ impl BaseCalendar for CachedCalendar {
     }
     #[cfg(feature = "local_calendar_mocks_remote_calendars")]
     async fn add_item(&mut self, item: Item) -> Result<SyncStatus, Box<dyn Error>> {
-        if self.is_mocking_remote_calendar {
+        #[cfg(feature = "local_calendar_mocks_remote_calendars")]
+        self.mock_behaviour.as_ref().map_or(Ok(()), |b| b.lock().unwrap().can_add_item())?;
+
+        if self.mock_behaviour.is_some() {
             self.add_item_force_synced(item).await
         } else {
             self.regular_add_item(item).await
@@ -121,7 +130,7 @@ impl CompleteCalendar for CachedCalendar {
         Self {
             name, id, supported_components,
             #[cfg(feature = "local_calendar_mocks_remote_calendars")]
-            is_mocking_remote_calendar: false,
+            mock_behaviour: None,
             items: HashMap::new(),
         }
     }
@@ -200,6 +209,9 @@ impl DavCalendar for CachedCalendar {
     }
 
     async fn get_item_version_tags(&self) -> Result<HashMap<ItemId, VersionTag>, Box<dyn Error>> {
+        #[cfg(feature = "local_calendar_mocks_remote_calendars")]
+        self.mock_behaviour.as_ref().map_or(Ok(()), |b| b.lock().unwrap().can_get_item_version_tags())?;
+
         use crate::item::SyncStatus;
 
         let mut result = HashMap::new();
@@ -218,10 +230,16 @@ impl DavCalendar for CachedCalendar {
     }
 
     async fn get_item_by_id(&self, id: &ItemId) -> Result<Option<Item>, Box<dyn Error>> {
+        #[cfg(feature = "local_calendar_mocks_remote_calendars")]
+        self.mock_behaviour.as_ref().map_or(Ok(()), |b| b.lock().unwrap().can_get_item_by_id())?;
+
         Ok(self.items.get(id).cloned())
     }
 
     async fn delete_item(&mut self, item_id: &ItemId) -> Result<(), Box<dyn Error>> {
+        #[cfg(feature = "local_calendar_mocks_remote_calendars")]
+        self.mock_behaviour.as_ref().map_or(Ok(()), |b| b.lock().unwrap().can_delete_item())?;
+
         self.immediately_delete_item(item_id).await
     }
 }

src/lib.rs

@@ -26,6 +26,7 @@ mod event;
 pub use event::Event;
 pub mod provider;
 pub use provider::Provider;
+pub mod mock_behaviour;
 
 pub mod client;
 pub use client::Client;

src/mock_behaviour.rs

@@ -0,0 +1,155 @@
+//! This module provides ways to tweak mocked calendars, so that they can return errors on some tests
+
+use std::error::Error;
+
+/// This stores some behaviour tweaks, that describe how a mocked instance will behave during a given test
+///
+/// So that a functions fails _n_ times after _m_ initial successes, set `(m, n)` for the suited parameter
+#[derive(Default, Clone, Debug)]
+pub struct MockBehaviour {
+    /// If this is true, every action will be allowed
+    pub is_suspended: bool,
+
+    // From the CalDavSource trait
+    pub get_calendars_behaviour: (u32, u32),
+    //pub get_calendar_behaviour: (u32, u32),
+    pub create_calendar_behaviour: (u32, u32),
+
+    // From the BaseCalendar trait
+    pub add_item_behaviour: (u32, u32),
+
+    // From the DavCalendar trait
+    pub get_item_version_tags_behaviour: (u32, u32),
+    pub get_item_by_id_behaviour: (u32, u32),
+    pub delete_item_behaviour: (u32, u32),
+}
+
+impl MockBehaviour {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// All items will fail at once, for `n_fails` times
+    pub fn fail_now(n_fails: u32) -> Self {
+        Self {
+            is_suspended: false,
+            get_calendars_behaviour: (0, n_fails),
+            //get_calendar_behaviour: (0, n_fails),
+            create_calendar_behaviour: (0, n_fails),
+            add_item_behaviour: (0, n_fails),
+            get_item_version_tags_behaviour: (0, n_fails),
+            get_item_by_id_behaviour: (0, n_fails),
+            delete_item_behaviour: (0, n_fails),
+        }
+    }
+
+    /// Suspend this mock behaviour until you call `resume`
+    pub fn suspend(&mut self) {
+        self.is_suspended = true;
+    }
+    /// Make this behaviour active again
+    pub fn resume(&mut self) {
+        self.is_suspended = false;
+    }
+
+    pub fn copy_from(&mut self, other: &Self) {
+        self.get_calendars_behaviour = other.get_calendars_behaviour;
+        self.create_calendar_behaviour = other.create_calendar_behaviour;
+    }
+
+    pub fn can_get_calendars(&mut self) -> Result<(), Box<dyn Error>> {
+        if self.is_suspended { return Ok(()) }
+        decrement(&mut self.get_calendars_behaviour, "get_calendars")
+    }
+    // pub fn can_get_calendar(&mut self) -> Result<(), Box<dyn Error>> {
+    //     if self.is_suspended { return Ok(()) }
+    //     decrement(&mut self.get_calendar_behaviour, "get_calendar")
+    // }
+    pub fn can_create_calendar(&mut self) -> Result<(), Box<dyn Error>> {
+        if self.is_suspended { return Ok(()) }
+        decrement(&mut self.create_calendar_behaviour, "create_calendar")
+    }
+    pub fn can_add_item(&mut self) -> Result<(), Box<dyn Error>> {
+        if self.is_suspended { return Ok(()) }
+        decrement(&mut self.add_item_behaviour, "add_item")
+    }
+    pub fn can_get_item_version_tags(&mut self) -> Result<(), Box<dyn Error>> {
+        if self.is_suspended { return Ok(()) }
+        decrement(&mut self.get_item_version_tags_behaviour, "get_item_version_tags")
+    }
+    pub fn can_get_item_by_id(&mut self) -> Result<(), Box<dyn Error>> {
+        if self.is_suspended { return Ok(()) }
+        decrement(&mut self.get_item_by_id_behaviour, "get_item_by_id")
+    }
+    pub fn can_delete_item(&mut self) -> Result<(), Box<dyn Error>> {
+        if self.is_suspended { return Ok(()) }
+        decrement(&mut self.delete_item_behaviour, "delete_item")
+    }
+}
+
+
+/// Return Ok(()) in case the value is `(1+, _)` or `(_, 0)`, or return Err and decrement otherwise
+fn decrement(value: &mut (u32, u32), descr: &str) -> Result<(), Box<dyn Error>> {
+    let remaining_successes = value.0;
+    let remaining_failures = value.1;
+
+    if remaining_successes > 0 {
+        value.0 = value.0 - 1;
+        log::debug!("Mock behaviour: allowing a {} ({:?})", descr, value);
+        Ok(())
+    } else {
+        if remaining_failures > 0 {
+            value.1 = value.1 - 1;
+            log::debug!("Mock behaviour: failing a {} ({:?})", descr, value);
+            Err(format!("Mocked behaviour requires this {} to fail this time. ({:?})", descr, value).into())
+        } else {
+            log::debug!("Mock behaviour: allowing a {} ({:?})", descr, value);
+            Ok(())
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_mock_behaviour() {
+        let mut ok = MockBehaviour::new();
+        assert!(ok.can_get_calendars().is_ok());
+        assert!(ok.can_get_calendars().is_ok());
+        assert!(ok.can_get_calendars().is_ok());
+        assert!(ok.can_get_calendars().is_ok());
+        assert!(ok.can_get_calendars().is_ok());
+        assert!(ok.can_get_calendars().is_ok());
+        assert!(ok.can_get_calendars().is_ok());
+
+        let mut now = MockBehaviour::fail_now(2);
+        assert!(now.can_get_calendars().is_err());
+        assert!(now.can_create_calendar().is_err());
+        assert!(now.can_create_calendar().is_err());
+        assert!(now.can_get_calendars().is_err());
+        assert!(now.can_get_calendars().is_ok());
+        assert!(now.can_get_calendars().is_ok());
+        assert!(now.can_create_calendar().is_ok());
+
+        let mut custom = MockBehaviour{
+            get_calendars_behaviour: (0,1),
+            create_calendar_behaviour: (1,3),
+            ..MockBehaviour::default()
+        };
+        assert!(custom.can_get_calendars().is_err());
+        assert!(custom.can_get_calendars().is_ok());
+        assert!(custom.can_get_calendars().is_ok());
+        assert!(custom.can_get_calendars().is_ok());
+        assert!(custom.can_get_calendars().is_ok());
+        assert!(custom.can_get_calendars().is_ok());
+        assert!(custom.can_get_calendars().is_ok());
+        assert!(custom.can_create_calendar().is_ok());
+        assert!(custom.can_create_calendar().is_err());
+        assert!(custom.can_create_calendar().is_err());
+        assert!(custom.can_create_calendar().is_err());
+        assert!(custom.can_create_calendar().is_ok());
+        assert!(custom.can_create_calendar().is_ok());
+    }
+}

src/provider.rs

@@ -10,6 +10,37 @@ use crate::traits::CompleteCalendar;
 use crate::item::SyncStatus;
 use crate::calendar::CalendarId;
 
+/// A counter of errors that happen during a sync
+struct SyncResult {
+    n_errors: u32,
+}
+impl SyncResult {
+    pub fn new() -> Self {
+        Self { n_errors: 0 }
+    }
+    pub fn is_success(&self) -> bool {
+        self.n_errors == 0
+    }
+
+    pub fn error(&mut self, text: &str) {
+        log::error!("{}", text);
+        self.n_errors += 1;
+    }
+    pub fn warn(&mut self, text: &str) {
+        log::warn!("{}", text);
+        self.n_errors += 1;
+    }
+    pub fn info(&mut self, text: &str) {
+        log::info!("{}", text);
+    }
+    pub fn debug(&mut self, text: &str) {
+        log::debug!("{}", text);
+    }
+    pub fn trace(&mut self, text: &str) {
+        log::trace!("{}", text);
+    }
+}
+
 /// A data source that combines two `CalDavSource`s (usually a server and a local cache), which is able to sync both sources.
 /// This can be used for integration tests, where the remote source is mocked by a `Cache`.
 pub struct Provider<L, T, R, U>
@@ -54,8 +85,19 @@ where
     ///
     /// This bidirectional sync applies additions/deletions made on a source to the other source.
     /// In case of conflicts (the same item has been modified on both ends since the last sync, `remote` always wins)
-    pub async fn sync(&mut self) -> Result<(), Box<dyn Error>> {
-        log::info!("Starting a sync.");
+    ///
+    /// It returns whether the sync was totally successful (details about errors are logged using the `log::*` macros).
+    /// In case errors happened, the sync might have been partially executed, and you can safely run this function again, since it has been designed to gracefully recover from errors.
+    pub async fn sync(&mut self) -> bool {
+        let mut result = SyncResult::new();
+        if let Err(err) = self.run_sync(&mut result).await {
+            result.error(&format!("Sync terminated because of an error: {}", err));
+        }
+        result.is_success()
+    }
+
+    async fn run_sync(&mut self, result: &mut SyncResult) -> Result<(), Box<dyn Error>> {
+        result.info("Starting a sync.");
 
         let mut handled_calendars = HashSet::new();
 
@@ -64,14 +106,14 @@ where
         for (cal_id, cal_remote) in cals_remote {
             let counterpart = match self.get_or_insert_local_counterpart_calendar(&cal_id, cal_remote.clone()).await {
                 Err(err) => {
-                    log::warn!("Unable to get or insert local counterpart calendar for {} ({}). Skipping this time", cal_id, err);
+                    result.warn(&format!("Unable to get or insert local counterpart calendar for {} ({}). Skipping this time", cal_id, err));
                     continue;
                 },
                 Ok(arc) => arc,
             };
 
-            if let Err(err) = Self::sync_calendar_pair(counterpart, cal_remote).await {
-                log::warn!("Unable to sync calendar {}: {}, skipping this time.", cal_id, err);
+            if let Err(err) = Self::sync_calendar_pair(counterpart, cal_remote, result).await {
+                result.warn(&format!("Unable to sync calendar {}: {}, skipping this time.", cal_id, err));
                 continue;
             }
             handled_calendars.insert(cal_id);
@@ -86,14 +128,14 @@ where
 
             let counterpart = match self.get_or_insert_remote_counterpart_calendar(&cal_id, cal_local.clone()).await {
                 Err(err) => {
-                    log::warn!("Unable to get or insert remote counterpart calendar for {} ({}). Skipping this time", cal_id, err);
+                    result.warn(&format!("Unable to get or insert remote counterpart calendar for {} ({}). Skipping this time", cal_id, err));
                     continue;
                 },
                 Ok(arc) => arc,
             };
 
-            if let Err(err) = Self::sync_calendar_pair(cal_local, counterpart).await {
-                log::warn!("Unable to sync calendar {}: {}, skipping this time.", cal_id, err);
+            if let Err(err) = Self::sync_calendar_pair(cal_local, counterpart, result).await {
+                result.warn(&format!("Unable to sync calendar {}: {}, skipping this time.", cal_id, err));
                 continue;
             }
         }
@@ -110,12 +152,12 @@ where
     }
 
 
-    async fn sync_calendar_pair(cal_local: Arc<Mutex<T>>, cal_remote: Arc<Mutex<U>>) -> Result<(), Box<dyn Error>> {
+    async fn sync_calendar_pair(cal_local: Arc<Mutex<T>>, cal_remote: Arc<Mutex<U>>, result: &mut SyncResult) -> Result<(), Box<dyn Error>> {
         let mut cal_remote = cal_remote.lock().unwrap();
         let mut cal_local = cal_local.lock().unwrap();
 
         // Step 1 - find the differences
-        log::debug!("Finding the differences to sync...");
+        result.debug("Finding the differences to sync...");
         let mut local_del = HashSet::new();
         let mut remote_del = HashSet::new();
         let mut local_changes = HashSet::new();
@@ -126,49 +168,49 @@ where
         let remote_items = cal_remote.get_item_version_tags().await?;
         let mut local_items_to_handle = cal_local.get_item_ids().await?;
         for (id, remote_tag) in remote_items {
-            log::trace!("***** Considering remote item {}...", id);
+            result.trace(&format!("***** Considering remote item {}...", id));
             match cal_local.get_item_by_id_ref(&id).await {
                 None => {
                     // This was created on the remote
-                    log::debug!("*   {} is a remote addition", id);
+                    result.debug(&format!("*   {} is a remote addition", id));
                     remote_additions.insert(id);
                 },
                 Some(local_item) => {
                     if local_items_to_handle.remove(&id) == false {
-                        log::error!("Inconsistent state: missing task {} from the local tasks", id);
+                        result.error(&format!("Inconsistent state: missing task {} from the local tasks", id));
                     }
 
                     match local_item.sync_status() {
                         SyncStatus::NotSynced => {
-                            log::error!("ID reuse between remote and local sources ({}). Ignoring this item in the sync", id);
+                            result.error(&format!("ID reuse between remote and local sources ({}). Ignoring this item in the sync", id));
                             continue;
                         },
                         SyncStatus::Synced(local_tag) => {
                             if &remote_tag != local_tag {
                                 // This has been modified on the remote
-                                log::debug!("*   {} is a remote change", id);
+                                result.debug(&format!("*   {} is a remote change", id));
                                 remote_changes.insert(id);
                             }
                         },
                         SyncStatus::LocallyModified(local_tag) => {
                             if &remote_tag == local_tag {
                                 // This has been changed locally
-                                log::debug!("*   {} is a local change", id);
+                                result.debug(&format!("*   {} is a local change", id));
                                 local_changes.insert(id);
                             } else {
-                                log::info!("Conflict: task {} has been modified in both sources. Using the remote version.", id);
-                                log::debug!("*   {} is considered a remote change", id);
+                                result.info(&format!("Conflict: task {} has been modified in both sources. Using the remote version.", id));
+                                result.debug(&format!("*   {} is considered a remote change", id));
                                 remote_changes.insert(id);
                             }
                         },
                         SyncStatus::LocallyDeleted(local_tag) => {
                             if &remote_tag == local_tag {
                                 // This has been locally deleted
-                                log::debug!("*   {} is a local deletion", id);
+                                result.debug(&format!("*   {} is a local deletion", id));
                                 local_del.insert(id);
                             } else {
-                                log::info!("Conflict: task {} has been locally deleted and remotely modified. Reverting to the remote version.", id);
-                                log::debug!("*   {} is a considered a remote change", id);
+                                result.info(&format!("Conflict: task {} has been locally deleted and remotely modified. Reverting to the remote version.", id));
+                                result.debug(&format!("*   {} is a considered a remote change", id));
                                 remote_changes.insert(id);
                             }
                         },
@@ -179,10 +221,10 @@ where
 
         // Also iterate on the local tasks that are not on the remote
         for id in local_items_to_handle {
-            log::trace!("##### Considering local item {}...", id);
+            result.trace(&format!("##### Considering local item {}...", id));
             let local_item = match cal_local.get_item_by_id_ref(&id).await {
                 None => {
-                    log::error!("Inconsistent state: missing task {} from the local tasks", id);
+                    result.error(&format!("Inconsistent state: missing task {} from the local tasks", id));
                     continue;
                 },
                 Some(item) => item,
@@ -191,21 +233,21 @@ where
             match local_item.sync_status() {
                 SyncStatus::Synced(_) => {
                     // This item has been removed from the remote
-                    log::debug!("#   {} is a deletion from the server", id);
+                    result.debug(&format!("#   {} is a deletion from the server", id));
                     remote_del.insert(id);
                 },
                 SyncStatus::NotSynced => {
                     // This item has just been locally created
-                    log::debug!("#   {} has been locally created", id);
+                    result.debug(&format!("#   {} has been locally created", id));
                     local_additions.insert(id);
                 },
                 SyncStatus::LocallyDeleted(_) => {
                     // This item has been deleted from both sources
-                    log::debug!("#   {} has been deleted from both sources", id);
+                    result.debug(&format!("#   {} has been deleted from both sources", id));
                     remote_del.insert(id);
                 },
                 SyncStatus::LocallyModified(_) => {
-                    log::info!("Conflict: item {} has been deleted from the server and locally modified. Deleting the local copy", id);
+                    result.info(&format!("Conflict: item {} has been deleted from the server and locally modified. Deleting the local copy", id));
                     remote_del.insert(id);
                 },
             }
@@ -213,44 +255,44 @@ where
 
 
         // Step 2 - commit changes
-        log::trace!("Committing changes...");
+        result.trace("Committing changes...");
         for id_del in local_del {
-            log::debug!("> Pushing local deletion {} to the server", id_del);
+            result.debug(&format!("> Pushing local deletion {} to the server", id_del));
             match cal_remote.delete_item(&id_del).await {
                 Err(err) => {
-                    log::warn!("Unable to delete remote item {}: {}", id_del, err);
+                    result.warn(&format!("Unable to delete remote item {}: {}", id_del, err));
                 },
                 Ok(()) => {
                     // Change the local copy from "marked to deletion" to "actually deleted"
                     if let Err(err) = cal_local.immediately_delete_item(&id_del).await {
-                        log::error!("Unable to permanently delete local item {}: {}", id_del, err);
+                        result.error(&format!("Unable to permanently delete local item {}: {}", id_del, err));
                     }
                 },
             }
         }
 
         for id_del in remote_del {
-            log::debug!("> Applying remote deletion {} locally", id_del);
+            result.debug(&format!("> Applying remote deletion {} locally", id_del));
             if let Err(err) = cal_local.immediately_delete_item(&id_del).await {
-                log::warn!("Unable to delete local item {}: {}", id_del, err);
+                result.warn(&format!("Unable to delete local item {}: {}", id_del, err));
             }
         }
 
         for id_add in remote_additions {
-            log::debug!("> Applying remote addition {} locally", id_add);
+            result.debug(&format!("> Applying remote addition {} locally", id_add));
             match cal_remote.get_item_by_id(&id_add).await {
                 Err(err) => {
-                    log::warn!("Unable to get remote item {}: {}. Skipping it.", id_add, err);
+                    result.warn(&format!("Unable to get remote item {}: {}. Skipping it.", id_add, err));
                     continue;
                 },
                 Ok(item) => match item {
                     None => {
-                        log::error!("Inconsistency: new item {} has vanished from the remote end", id_add);
+                        result.error(&format!("Inconsistency: new item {} has vanished from the remote end", id_add));
                         continue;
                     },
                     Some(new_item) => {
                         if let Err(err) = cal_local.add_item(new_item.clone()).await {
-                            log::error!("Not able to add item {} to local calendar: {}", id_add, err);
+                            result.error(&format!("Not able to add item {} to local calendar: {}", id_add, err));
                         }
                     },
                 },
@@ -258,15 +300,15 @@ where
         }
 
         for id_change in remote_changes {
-            log::debug!("> Applying remote change {} locally", id_change);
+            result.debug(&format!("> Applying remote change {} locally", id_change));
             match cal_remote.get_item_by_id(&id_change).await {
                 Err(err) => {
-                    log::warn!("Unable to get remote item {}: {}. Skipping it", id_change, err);
+                    result.warn(&format!("Unable to get remote item {}: {}. Skipping it", id_change, err));
                     continue;
                 },
                 Ok(item) => match item {
                     None => {
-                        log::error!("Inconsistency: modified item {} has vanished from the remote end", id_change);
+                        result.error(&format!("Inconsistency: modified item {} has vanished from the remote end", id_change));
                         continue;
                     },
                     Some(item) => {
@@ -277,10 +319,10 @@ where
                         // TODO: implement update_item (maybe only create_item also updates it?)
                         //
                         if let Err(err) = cal_local.immediately_delete_item(&id_change).await {
-                            log::error!("Unable to delete item {} from local calendar: {}", id_change, err);
+                            result.error(&format!("Unable to delete item {} from local calendar: {}", id_change, err));
                         }
                         if let Err(err) = cal_local.add_item(item.clone()).await {
-                            log::error!("Unable to add item {} to local calendar: {}", id_change, err);
+                            result.error(&format!("Unable to add item {} to local calendar: {}", id_change, err));
                         }
                     },
                 }
@@ -289,15 +331,15 @@ where
 
 
         for id_add in local_additions {
-            log::debug!("> Pushing local addition {} to the server", id_add);
+            result.debug(&format!("> Pushing local addition {} to the server", id_add));
             match cal_local.get_item_by_id_mut(&id_add).await {
                 None => {
-                    log::error!("Inconsistency: created item {} has been marked for upload but is locally missing", id_add);
+                    result.error(&format!("Inconsistency: created item {} has been marked for upload but is locally missing", id_add));
                     continue;
                 },
                 Some(item) => {
                     match cal_remote.add_item(item.clone()).await {
-                        Err(err) => log::error!("Unable to add item {} to remote calendar: {}", id_add, err),
+                        Err(err) => result.error(&format!("Unable to add item {} to remote calendar: {}", id_add, err)),
                         Ok(new_ss) => {
                             // Update local sync status
                             item.set_sync_status(new_ss);
@@ -308,10 +350,10 @@ where
         }
 
         for id_change in local_changes {
-            log::debug!("> Pushing local change {} to the server", id_change);
+            result.debug(&format!("> Pushing local change {} to the server", id_change));
             match cal_local.get_item_by_id_mut(&id_change).await {
                 None => {
-                    log::error!("Inconsistency: modified item {} has been marked for upload but is locally missing", id_change);
+                    result.error(&format!("Inconsistency: modified item {} has been marked for upload but is locally missing", id_change));
                     continue;
                 },
                 Some(item) => {
@@ -322,7 +364,7 @@ where
                     // TODO: implement update_item (maybe only create_item also updates it?)
                     //
                     if let Err(err) = cal_remote.delete_item(&id_change).await {
-                        log::error!("Unable to delete item {} from remote calendar: {}", id_change, err);
+                        result.error(&format!("Unable to delete item {} from remote calendar: {}", id_change, err));
                     }
                     match cal_remote.add_item(item.clone()).await {
                         Err(err) => log::error!("Unable to add item {} to remote calendar: {}", id_change, err),

tests/scenarii.rs

@@ -25,6 +25,7 @@ use my_tasks::SyncStatus;
 use my_tasks::Task;
 use my_tasks::calendar::cached_calendar::CachedCalendar;
 use my_tasks::Provider;
+use my_tasks::mock_behaviour::MockBehaviour;
 
 pub enum LocatedState {
     /// Item does not exist yet or does not exist anymore
@@ -575,21 +576,21 @@ pub fn scenarii_transient_task() -> Vec<ItemScenario> {
 
 
 /// Build a `Provider` that contains the data (defined in the given scenarii) before sync
-pub async fn populate_test_provider_before_sync(scenarii: &[ItemScenario]) -> Provider<Cache, CachedCalendar, Cache, CachedCalendar> {
-    let mut provider = populate_test_provider(scenarii, false).await;
+pub async fn populate_test_provider_before_sync(scenarii: &[ItemScenario], mock_behaviour: Arc<Mutex<MockBehaviour>>) -> Provider<Cache, CachedCalendar, Cache, CachedCalendar> {
+    let mut provider = populate_test_provider(scenarii, mock_behaviour, false).await;
     apply_changes_on_provider(&mut provider, scenarii).await;
     provider
 }
 
 /// Build a `Provider` that contains the data (defined in the given scenarii) after sync
-pub async fn populate_test_provider_after_sync(scenarii: &[ItemScenario]) -> Provider<Cache, CachedCalendar, Cache, CachedCalendar> {
-    populate_test_provider(scenarii, true).await
+pub async fn populate_test_provider_after_sync(scenarii: &[ItemScenario], mock_behaviour: Arc<Mutex<MockBehaviour>>) -> Provider<Cache, CachedCalendar, Cache, CachedCalendar> {
+    populate_test_provider(scenarii, mock_behaviour, true).await
 }
 
-async fn populate_test_provider(scenarii: &[ItemScenario], populate_for_final_state: bool) -> Provider<Cache, CachedCalendar, Cache, CachedCalendar> {
+async fn populate_test_provider(scenarii: &[ItemScenario], mock_behaviour: Arc<Mutex<MockBehaviour>>, populate_for_final_state: bool) -> Provider<Cache, CachedCalendar, Cache, CachedCalendar> {
     let mut local = Cache::new(&PathBuf::from(String::from("test_cache_local/")));
     let mut remote = Cache::new(&PathBuf::from(String::from("test_cache_remote/")));
-    remote.set_is_mocking_remote_source();
+    remote.set_mock_behaviour(Some(mock_behaviour));
 
     // Create the initial state, as if we synced both sources in a given state
     for item in scenarii {

tests/sync.rs

@@ -1,5 +1,10 @@
 mod scenarii;
 
+#[cfg(feature = "local_calendar_mocks_remote_calendars")]
+use std::sync::{Arc, Mutex};
+
+#[cfg(feature = "local_calendar_mocks_remote_calendars")]
+use my_tasks::mock_behaviour::MockBehaviour;
 
 
 
@@ -8,6 +13,8 @@ mod scenarii;
 struct TestFlavour {
     #[cfg(feature = "local_calendar_mocks_remote_calendars")]
     scenarii: Vec<scenarii::ItemScenario>,
+    #[cfg(feature = "local_calendar_mocks_remote_calendars")]
+    mock_behaviour: Arc<Mutex<MockBehaviour>>,
 }
 
 #[cfg(not(feature = "local_calendar_mocks_remote_calendars"))]
@@ -16,8 +23,9 @@ impl TestFlavour {
     pub fn first_sync_to_local() -> Self { Self{} }
     pub fn first_sync_to_server() -> Self { Self{} }
     pub fn transient_task() -> Self { Self{} }
+    pub fn normal_with_errors() -> Self { Self{} }
 
-    pub async fn run(&self) {
+    pub async fn run(&self, _max_attempts: u32) {
         println!("WARNING: This test required the \"integration_tests\" Cargo feature");
     }
 }
@@ -27,34 +35,54 @@ impl TestFlavour {
     pub fn normal() -> Self {
         Self {
             scenarii: scenarii::scenarii_basic(),
+            mock_behaviour: Arc::new(Mutex::new(MockBehaviour::new())),
         }
     }
 
     pub fn first_sync_to_local() -> Self {
         Self {
             scenarii: scenarii::scenarii_first_sync_to_local(),
+            mock_behaviour: Arc::new(Mutex::new(MockBehaviour::new())),
         }
     }
 
     pub fn first_sync_to_server() -> Self {
         Self {
             scenarii: scenarii::scenarii_first_sync_to_server(),
+            mock_behaviour: Arc::new(Mutex::new(MockBehaviour::new())),
         }
     }
 
     pub fn transient_task() -> Self {
         Self {
             scenarii: scenarii::scenarii_transient_task(),
+            mock_behaviour: Arc::new(Mutex::new(MockBehaviour::new())),
         }
     }
 
-    pub async fn run(&self) {
-        let mut provider = scenarii::populate_test_provider_before_sync(&self.scenarii).await;
+    pub fn normal_with_errors() -> Self {
+        Self {
+            scenarii: scenarii::scenarii_basic(),
+            mock_behaviour: Arc::new(Mutex::new(MockBehaviour::fail_now(10))),
+        }
+    }
 
+
+    pub async fn run(&self, max_attempts: u32) {
+        self.mock_behaviour.lock().unwrap().suspend();
+
+        let mut provider = scenarii::populate_test_provider_before_sync(&self.scenarii, Arc::clone(&self.mock_behaviour)).await;
         print_provider(&provider, "before sync").await;
 
-        println!("\nsyncing...\n");
-        provider.sync().await.unwrap();
+        self.mock_behaviour.lock().unwrap().resume();
+        for attempt in 0..max_attempts {
+            println!("\nSyncing...\n");
+            if provider.sync().await == true {
+                println!("Sync complete after {} attempts (multiple attempts are due to forced errors in mocked behaviour)", attempt+1);
+                break
+            }
+        }
+        self.mock_behaviour.lock().unwrap().suspend();
 
         print_provider(&provider, "after sync").await;
 
@@ -62,7 +90,7 @@ impl TestFlavour {
         assert!(provider.remote().has_same_observable_content_as(provider.local()).await.unwrap());
 
         // But also explicitely check that every item is expected
-        let expected_provider = scenarii::populate_test_provider_after_sync(&self.scenarii).await;
+        let expected_provider = scenarii::populate_test_provider_after_sync(&self.scenarii, Arc::clone(&self.mock_behaviour)).await;
         println!("\n");
         print_provider(&expected_provider, "expected after sync").await;
 
@@ -71,7 +99,7 @@ impl TestFlavour {
 
         // Perform a second sync, even if no change has happened, just to check
         println!("Syncing again");
-        provider.sync().await.unwrap();
+        provider.sync().await;
         assert!(provider.local() .has_same_observable_content_as(expected_provider.local() ).await.unwrap());
         assert!(provider.remote().has_same_observable_content_as(expected_provider.remote()).await.unwrap());
     }
@@ -85,7 +113,7 @@ async fn test_regular_sync() {
     let _ = env_logger::builder().is_test(true).try_init();
 
     let flavour = TestFlavour::normal();
-    flavour.run().await;
+    flavour.run(1).await;
 }
 
 #[tokio::test]
@@ -93,7 +121,7 @@ async fn test_sync_empty_initial_local() {
     let _ = env_logger::builder().is_test(true).try_init();
 
     let flavour = TestFlavour::first_sync_to_local();
-    flavour.run().await;
+    flavour.run(1).await;
 }
 
 #[tokio::test]
@@ -101,7 +129,7 @@ async fn test_sync_empty_initial_server() {
     let _ = env_logger::builder().is_test(true).try_init();
 
     let flavour = TestFlavour::first_sync_to_server();
-    flavour.run().await;
+    flavour.run(1).await;
 }
 
 #[tokio::test]
@@ -109,9 +137,16 @@ async fn test_sync_transient_task() {
     let _ = env_logger::builder().is_test(true).try_init();
 
     let flavour = TestFlavour::transient_task();
-    flavour.run().await;
+    flavour.run(1).await;
 }
 
+#[tokio::test]
+async fn test_errors_in_regular_sync() {
+    let _ = env_logger::builder().is_test(true).try_init();
+
+    let flavour = TestFlavour::normal_with_errors();
+    flavour.run(100).await;
+}
 
 #[cfg(feature = "integration_tests")]
 use my_tasks::{traits::CalDavSource,