diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..1f7412e
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,29 @@
+from pathlib import Path
+from typing import List, Callable
+
+import pytest
+
+from intake.source import LocalSource
+
+
+def clean_source(source_path: Path):
+    for item in source_path.iterdir():
+        if item.name.endswith(".item"):
+            item.unlink()
+    (source_path / "state").unlink(missing_ok=True)
+
+
+@pytest.fixture
+def using_source() -> Callable:
+    test_data = Path(__file__).parent
+    sources: List[Path] = []
+
+    def _using_source(name: str):
+        source_path = test_data / name
+        clean_source(source_path)
+        sources.append(source_path)
+        return LocalSource(test_data, name)
+    yield _using_source
+
+    for source_path in sources:
+        clean_source(source_path)
diff --git a/tests/default/intake.json b/tests/default/intake.json
new file mode 100644
index 0000000..8feca31
--- /dev/null
+++ b/tests/default/intake.json
@@ -0,0 +1,7 @@
+{
+  "action": {
+    "fetch": {
+      "exe": "true"
+    }
+  }
+}
\ No newline at end of file
diff --git a/tests/demo_basic_callback/increment.py b/tests/demo_basic_callback/increment.py
index 6a062c6..654622a 100755
--- a/tests/demo_basic_callback/increment.py
+++ b/tests/demo_basic_callback/increment.py
@@ -9,14 +9,18 @@ args = parser.parse_args()
 print("args:", args, file=sys.stderr, flush=True)
 
 if args.action == "fetch":
-    print(json.dumps({
-        "id": "updateme",
-        "title": "The count is at 1",
-        "action": {
-            "increment": 1,
-            "decrement": "",
-        }
-    }))
+    print(
+        json.dumps(
+            {
+                "id": "updateme",
+                "title": "The count is at 1",
+                "action": {
+                    "increment": 1,
+                    "decrement": "",
+                },
+            }
+        )
+    )
 
 if args.action == "increment":
     item = sys.stdin.readline()
diff --git a/tests/demo_logging/update.py b/tests/demo_logging/update.py
index f4e820f..aa9790d 100755
--- a/tests/demo_logging/update.py
+++ b/tests/demo_logging/update.py
@@ -6,10 +6,7 @@ import sys
 import time
 
 greeting = os.environ.get("HELLO", "MISSING")
-item = json.dumps({
-    "id": "helloworld",
-    "title": "Hello = " + greeting
-})
+item = json.dumps({"id": "helloworld", "title": "Hello = " + greeting})
 sys.stdout.write(item[:10])
 sys.stdout.flush()
 
diff --git a/tests/test_inbox/intake.json b/tests/test_inbox/intake.json
new file mode 100644
index 0000000..a8c70a3
--- /dev/null
+++ b/tests/test_inbox/intake.json
@@ -0,0 +1,8 @@
+{
+  "action": {
+    "fetch": {
+      "exe": "./update.py",
+      "args": ["fetch"]
+    }
+  }
+}
\ No newline at end of file
diff --git a/tests/test_inbox/update.py b/tests/test_inbox/update.py
new file mode 100755
index 0000000..3abcc5d
--- /dev/null
+++ b/tests/test_inbox/update.py
@@ -0,0 +1,21 @@
+#!/usr/bin/env python3
+
+"""
+A test source that "generates" items by returning them from the state file.
+This source exists for unit testing so that unit tests can easily manipulate
+what items are returned by writing them to the state file directly.
+"""
+
+import argparse, json, os, sys
+
+parser = argparse.ArgumentParser()
+parser.add_argument("action")
+args = parser.parse_args()
+print("args:", args, file=sys.stderr, flush=True)
+
+if args.action == "fetch":
+    state_path = os.environ.get("STATE_PATH")
+    with open(state_path) as f:
+        state = json.load(f)
+    for item in state["inbox"]:
+        print(json.dumps(item))
diff --git a/tests/test_source.py b/tests/test_source.py
new file mode 100644
index 0000000..ba439e8
--- /dev/null
+++ b/tests/test_source.py
@@ -0,0 +1,63 @@
+import json
+
+from intake.source import fetch_items, update_items, LocalSource
+
+
+def test_default_source(using_source):
+    source: LocalSource = using_source("default")
+    fetch = fetch_items(source)
+    assert len(fetch) == 0
+
+def test_basic_lifecycle(using_source):
+    source: LocalSource = using_source("test_inbox")
+    state = {"inbox": [{"id": "first"}]}
+    source.get_state_path().write_text(json.dumps(state))
+
+    # The inboxed item is returned from fetch
+    fetch = fetch_items(source)
+    assert len(fetch) == 1
+    assert fetch[0]["id"] == "first"
+
+    # Update creates the item in the source
+    update_items(source, fetch)
+    assert source.get_item_path("first").exists()
+    assert source.get_item("first").get("active") == True
+    items = list(source.get_all_items())
+    assert len(items) == 1
+    assert items[0]["id"] == "first"
+
+    # A second fetch does not change anything
+    fetch = fetch_items(source)
+    update_items(source, fetch)
+    assert source.get_item_path("first").exists()
+    assert source.get_item("first").get("active") == True
+    items = list(source.get_all_items())
+    assert len(items) == 1
+    assert items[0]["id"] == "first"
+
+    # The item remains after it is no longer in the feed
+    state = {"inbox": [{"id": "second"}]}
+    source.get_state_path().write_text(json.dumps(state))
+
+    fetch = fetch_items(source)
+    update_items(source, fetch)
+    assert source.get_item_path("first").exists()
+    assert source.get_item("first").get("active") == True
+    assert source.get_item_path("second").exists()
+    assert source.get_item("second").get("active") == True
+    items = list(source.get_all_items())
+    assert len(items) == 2
+    assert sorted(map(lambda i: i["id"], items)) == ["first", "second"]
+
+    # The item is removed on the next update when it is inactive
+    first = source.get_item("first")
+    first["active"] = False
+    source.save_item(first)
+
+    fetch = fetch_items(source)
+    update_items(source, fetch)
+    assert not source.get_item_path("first").exists()
+    assert source.get_item_path("second").exists()
+    items = list(source.get_all_items())
+    assert len(items) == 1
+    assert items[0]["id"] == "second"