diff --git a/src/imfs/mod.rs b/src/imfs/mod.rs
index e930e089..58f51719 100644
--- a/src/imfs/mod.rs
+++ b/src/imfs/mod.rs
@@ -13,3 +13,9 @@ pub use imfs::*;
 pub use noop_fetcher::*;
 pub use real_fetcher::*;
 pub use snapshot::*;
+
+#[cfg(test)]
+mod test_fetcher;
+
+#[cfg(test)]
+pub use test_fetcher::*;
diff --git a/src/imfs/test_fetcher.rs b/src/imfs/test_fetcher.rs
new file mode 100644
index 00000000..96936415
--- /dev/null
+++ b/src/imfs/test_fetcher.rs
@@ -0,0 +1,175 @@
+//! Implements the IMFS fetcher interface for a fake filesystem that can be
+//! mutated and have changes signaled through it.
+//!
+//! This is useful for testing how things using Imfs react to changed events
+//! without relying on the real filesystem implementation, which is very
+//! platform-specific.
+
+// This interface is only used for testing, so it's okay if it isn't used.
+#![allow(unused)]
+
+use std::{
+    io,
+    path::{self, Path, PathBuf},
+    sync::{Arc, Mutex},
+};
+
+use crossbeam_channel::{unbounded, Receiver, Sender};
+
+use crate::path_map::PathMap;
+
+use super::{
+    event::ImfsEvent,
+    fetcher::{FileType, ImfsFetcher},
+    snapshot::ImfsSnapshot,
+};
+
+#[derive(Clone)]
+pub struct TestFetcherState {
+    inner: Arc<Mutex<TestFetcherStateInner>>,
+}
+
+impl TestFetcherState {
+    pub fn load_snapshot<P: AsRef<Path>>(&self, path: P, snapshot: ImfsSnapshot) {
+        let mut inner = self.inner.lock().unwrap();
+        inner.load_snapshot(path.as_ref().to_path_buf(), snapshot);
+    }
+
+    pub fn remove<P: AsRef<Path>>(&self, path: P) {
+        let mut inner = self.inner.lock().unwrap();
+        inner.remove(path.as_ref());
+    }
+
+    pub fn raise_event(&self, event: ImfsEvent) {
+        let mut inner = self.inner.lock().unwrap();
+        inner.raise_event(event);
+    }
+}
+
+pub enum TestFetcherEntry {
+    File(Vec<u8>),
+    Dir,
+}
+
+struct TestFetcherStateInner {
+    entries: PathMap<TestFetcherEntry>,
+    sender: Sender<ImfsEvent>,
+}
+
+impl TestFetcherStateInner {
+    fn new(sender: Sender<ImfsEvent>) -> Self {
+        let mut entries = PathMap::new();
+        entries.insert(Path::new("/"), TestFetcherEntry::Dir);
+
+        Self { sender, entries }
+    }
+
+    fn load_snapshot(&mut self, path: PathBuf, snapshot: ImfsSnapshot) {
+        match snapshot {
+            ImfsSnapshot::File(file) => {
+                self.entries
+                    .insert(path, TestFetcherEntry::File(file.contents));
+            }
+            ImfsSnapshot::Directory(directory) => {
+                self.entries.insert(path.clone(), TestFetcherEntry::Dir);
+
+                for (child_name, child) in directory.children.into_iter() {
+                    self.load_snapshot(path.join(child_name), child);
+                }
+            }
+        }
+    }
+
+    fn remove(&mut self, path: &Path) {
+        self.entries.remove(path);
+    }
+
+    fn raise_event(&mut self, event: ImfsEvent) {
+        self.sender.send(event).unwrap();
+    }
+}
+
+pub struct TestFetcher {
+    state: TestFetcherState,
+    receiver: Receiver<ImfsEvent>,
+}
+
+impl TestFetcher {
+    pub fn new() -> (TestFetcherState, Self) {
+        let (sender, receiver) = unbounded();
+
+        let state = TestFetcherState {
+            inner: Arc::new(Mutex::new(TestFetcherStateInner::new(sender))),
+        };
+
+        (state.clone(), Self { receiver, state })
+    }
+}
+
+impl ImfsFetcher for TestFetcher {
+    fn file_type(&mut self, path: &Path) -> io::Result<FileType> {
+        let inner = self.state.inner.lock().unwrap();
+
+        match inner.entries.get(path) {
+            Some(TestFetcherEntry::File(_)) => Ok(FileType::File),
+            Some(TestFetcherEntry::Dir) => Ok(FileType::Directory),
+            None => Err(io::Error::new(io::ErrorKind::NotFound, "Path not found")),
+        }
+    }
+
+    fn read_children(&mut self, path: &Path) -> io::Result<Vec<PathBuf>> {
+        let inner = self.state.inner.lock().unwrap();
+
+        Ok(inner
+            .entries
+            .children(path)
+            .ok_or_else(|| io::Error::new(io::ErrorKind::NotFound, "Path not found"))?
+            .into_iter()
+            .map(|path| path.to_path_buf())
+            .collect())
+    }
+
+    fn read_contents(&mut self, path: &Path) -> io::Result<Vec<u8>> {
+        let inner = self.state.inner.lock().unwrap();
+
+        let node = inner.entries.get(path);
+
+        match node {
+            Some(TestFetcherEntry::File(contents)) => Ok(contents.clone()),
+            Some(TestFetcherEntry::Dir) => Err(io::Error::new(
+                io::ErrorKind::Other,
+                "Cannot read contents of a directory",
+            )),
+            None => Err(io::Error::new(io::ErrorKind::NotFound, "Path not found")),
+        }
+    }
+
+    fn create_directory(&mut self, _path: &Path) -> io::Result<()> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "TestFetcher is not mutable yet",
+        ))
+    }
+
+    fn write_file(&mut self, _path: &Path, _contents: &[u8]) -> io::Result<()> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "TestFetcher is not mutable yet",
+        ))
+    }
+
+    fn remove(&mut self, _path: &Path) -> io::Result<()> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "TestFetcher is not mutable yet",
+        ))
+    }
+
+    fn watch(&mut self, _path: &Path) {}
+
+    fn unwatch(&mut self, _path: &Path) {}
+
+    fn receiver(&self) -> Receiver<ImfsEvent> {
+        self.receiver.clone()
+    }
+}