diff --git a/.coverage b/.coverage
new file mode 100644
index 0000000..4e68f72
Binary files /dev/null and b/.coverage differ
diff --git a/requirements.txt b/requirements.txt
index 5d9efb5..f2821b2 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,5 @@
 fastapi
 uvicorn
 httpx
-watchfiles
\ No newline at end of file
+watchfiles
+pytest
\ No newline at end of file
diff --git a/src/app.py b/src/app.py
index 4ebb1d9..ff2bd4a 100644
--- a/src/app.py
+++ b/src/app.py
@@ -38,6 +38,42 @@
         "schedule": "Mondays, Wednesdays, Fridays, 2:00 PM - 3:00 PM",
         "max_participants": 30,
         "participants": ["john@mergington.edu", "olivia@mergington.edu"]
+    },
+    "Basketball Team": {
+        "description": "Competitive basketball training and tournaments",
+        "schedule": "Mondays and Thursdays, 4:00 PM - 5:30 PM",
+        "max_participants": 15,
+        "participants": ["james@mergington.edu"]
+    },
+    "Tennis Club": {
+        "description": "Learn tennis skills and compete in matches",
+        "schedule": "Tuesdays and Saturdays, 3:30 PM - 5:00 PM",
+        "max_participants": 12,
+        "participants": ["isabella@mergington.edu"]
+    },
+    "Art Studio": {
+        "description": "Explore painting, drawing, and sculpture techniques",
+        "schedule": "Wednesdays, 3:30 PM - 5:00 PM",
+        "max_participants": 18,
+        "participants": ["lucas@mergington.edu", "ava@mergington.edu"]
+    },
+    "Drama Club": {
+        "description": "Theatre arts, script writing, and stage performances",
+        "schedule": "Fridays, 4:00 PM - 5:30 PM",
+        "max_participants": 25,
+        "participants": ["noah@mergington.edu"]
+    },
+    "Debate Team": {
+        "description": "Develop public speaking and critical thinking skills",
+        "schedule": "Mondays and Wednesdays, 3:30 PM - 4:30 PM",
+        "max_participants": 16,
+        "participants": ["mia@mergington.edu", "ethan@mergington.edu"]
+    },
+    "Science Club": {
+        "description": "Conduct experiments and explore scientific concepts",
+        "schedule": "Tuesdays, 3:30 PM - 5:00 PM",
+        "max_participants": 20,
+        "participants": ["charlotte@mergington.edu"]
     }
 }
 
@@ -62,6 +98,29 @@ def signup_for_activity(activity_name: str, email: str):
     # Get the specific activity
     activity = activities[activity_name]
 
+    # Validate student is not already signed up    
+    if email in activity["participants"]:
+        raise HTTPException(status_code=400, detail="Student already signed up for this activity")
+    
+
     # Add student
     activity["participants"].append(email)
     return {"message": f"Signed up {email} for {activity_name}"}
+
+
+@app.delete("/activities/{activity_name}/participants/{email}")
+def unregister_from_activity(activity_name: str, email: str):
+    """Unregister a student from an activity"""
+    # Validate activity exists
+    if activity_name not in activities:
+        raise HTTPException(status_code=404, detail="Activity not found")
+
+    activity = activities[activity_name]
+
+    # Check if participant is registered
+    if email not in activity["participants"]:
+        raise HTTPException(status_code=404, detail="Participant not found")
+
+    # Remove participant
+    activity["participants"].remove(email)
+    return {"message": f"Unregistered {email} from {activity_name}"}
diff --git a/src/static/app.js b/src/static/app.js
index dcc1e38..9a30179 100644
--- a/src/static/app.js
+++ b/src/static/app.js
@@ -25,10 +25,53 @@ document.addEventListener("DOMContentLoaded", () => {
           <p>${details.description}</p>
           <p><strong>Schedule:</strong> ${details.schedule}</p>
           <p><strong>Availability:</strong> ${spotsLeft} spots left</p>
+          <div class="participants-section">
+            <p><strong>Participants (${details.participants.length}/${details.max_participants}):</strong></p>
+            <ul class="participants-list">
+              ${details.participants.map(p => `<li><span class="participant-email">${p}</span><button class="delete-participant-btn" data-email="${p}" data-activity="${name}" type="button">×</button></li>`).join('')}
+            </ul>
+          </div>
         `;
 
         activitiesList.appendChild(activityCard);
 
+        // Add delete event listeners to participant buttons
+        const deleteButtons = activityCard.querySelectorAll(".delete-participant-btn");
+        deleteButtons.forEach(btn => {
+          btn.addEventListener("click", async (e) => {
+            e.preventDefault();
+            const email = btn.getAttribute("data-email");
+            const activity = btn.getAttribute("data-activity");
+
+            try {
+              const response = await fetch(
+                `/activities/${encodeURIComponent(activity)}/participants/${encodeURIComponent(email)}`,
+                { method: "DELETE" }
+              );
+
+              if (response.ok) {
+                // Refresh activities list after successful deletion
+                fetchActivities();
+                messageDiv.textContent = `Unregistered ${email} from ${activity}`;
+                messageDiv.className = "success";
+              } else {
+                const result = await response.json();
+                messageDiv.textContent = result.detail || "Failed to unregister";
+                messageDiv.className = "error";
+              }
+              messageDiv.classList.remove("hidden");
+              setTimeout(() => {
+                messageDiv.classList.add("hidden");
+              }, 5000);
+            } catch (error) {
+              messageDiv.textContent = "Failed to unregister. Please try again.";
+              messageDiv.className = "error";
+              messageDiv.classList.remove("hidden");
+              console.error("Error unregistering:", error);
+            }
+          });
+        });
+
         // Add option to select dropdown
         const option = document.createElement("option");
         option.value = name;
@@ -62,6 +105,7 @@ document.addEventListener("DOMContentLoaded", () => {
         messageDiv.textContent = result.message;
         messageDiv.className = "success";
         signupForm.reset();
+        fetchActivities();
       } else {
         messageDiv.textContent = result.detail || "An error occurred";
         messageDiv.className = "error";
diff --git a/src/static/styles.css b/src/static/styles.css
index a533b32..5fbe2b8 100644
--- a/src/static/styles.css
+++ b/src/static/styles.css
@@ -74,6 +74,61 @@ section h3 {
   margin-bottom: 8px;
 }
 
+.participants-section {
+  margin-top: 15px;
+  padding-top: 15px;
+  border-top: 1px solid #e0e0e0;
+}
+
+.participants-section p {
+  margin-bottom: 10px;
+  color: #555;
+  font-size: 14px;
+}
+
+.participants-list {
+  list-style: none;
+  margin-left: 0;
+  font-size: 13px;
+  color: #666;
+}
+
+.participants-list li {
+  margin-bottom: 5px;
+  padding: 4px 8px;
+  background-color: #f0f7ff;
+  border-radius: 3px;
+  border-left: 3px solid #0066cc;
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+}
+
+.participant-email {
+  flex-grow: 1;
+}
+
+.delete-participant-btn {
+  background: none;
+  border: none;
+  color: #c62828;
+  font-size: 20px;
+  line-height: 1;
+  cursor: pointer;
+  padding: 0 4px;
+  margin-left: 8px;
+  transition: color 0.2s, transform 0.1s;
+}
+
+.delete-participant-btn:hover {
+  color: #d32f2f;
+  transform: scale(1.2);
+}
+
+.delete-participant-btn:active {
+  transform: scale(0.95);
+}
+
 .form-group {
   margin-bottom: 15px;
 }
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..739954c
--- /dev/null
+++ b/tests/__init__.py
@@ -0,0 +1 @@
+# Tests package
\ No newline at end of file
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..3bbdb25
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,9 @@
+import pytest
+from fastapi.testclient import TestClient
+from src.app import app
+
+
+@pytest.fixture
+def client():
+    """Test client fixture for FastAPI app testing."""
+    return TestClient(app)
\ No newline at end of file
diff --git a/tests/test_activities.py b/tests/test_activities.py
new file mode 100644
index 0000000..6a8dac2
--- /dev/null
+++ b/tests/test_activities.py
@@ -0,0 +1,60 @@
+"""Tests for GET /activities endpoint."""
+
+
+def test_get_activities_returns_all_activities(client):
+    """Test that GET /activities returns all activities with correct structure."""
+    # Arrange: No specific setup needed as activities are predefined in app
+
+    # Act: Make GET request to /activities
+    response = client.get("/activities")
+
+    # Assert: Response status is 200
+    assert response.status_code == 200
+
+    # Assert: Response contains all 9 activities
+    activities = response.json()
+    assert len(activities) == 9
+
+    # Assert: Each activity has the expected structure
+    expected_activities = [
+        "Chess Club", "Programming Class", "Gym Class", "Basketball Team",
+        "Tennis Club", "Art Studio", "Drama Club", "Debate Team", "Science Club"
+    ]
+    assert set(activities.keys()) == set(expected_activities)
+
+    # Assert: Each activity has required fields
+    for activity_name, activity_data in activities.items():
+        assert "description" in activity_data
+        assert "schedule" in activity_data
+        assert "max_participants" in activity_data
+        assert "participants" in activity_data
+        assert isinstance(activity_data["participants"], list)
+
+
+def test_get_activities_participant_counts(client):
+    """Test that participant counts are correct for each activity."""
+    # Arrange: No specific setup needed
+
+    # Act: Make GET request to /activities
+    response = client.get("/activities")
+
+    # Assert: Response is successful
+    assert response.status_code == 200
+
+    activities = response.json()
+
+    # Assert: Specific participant counts match expected values
+    expected_counts = {
+        "Chess Club": 2,  # michael@mergington.edu, daniel@mergington.edu
+        "Programming Class": 2,  # emma@mergington.edu, sophia@mergington.edu
+        "Gym Class": 2,  # john@mergington.edu, olivia@mergington.edu
+        "Basketball Team": 1,  # james@mergington.edu
+        "Tennis Club": 1,  # isabella@mergington.edu
+        "Art Studio": 2,  # lucas@mergington.edu, ava@mergington.edu
+        "Drama Club": 1,  # noah@mergington.edu
+        "Debate Team": 2,  # mia@mergington.edu, ethan@mergington.edu
+        "Science Club": 1,  # charlotte@mergington.edu
+    }
+
+    for activity_name, expected_count in expected_counts.items():
+        assert len(activities[activity_name]["participants"]) == expected_count
\ No newline at end of file
diff --git a/tests/test_signup.py b/tests/test_signup.py
new file mode 100644
index 0000000..9e8e054
--- /dev/null
+++ b/tests/test_signup.py
@@ -0,0 +1,64 @@
+"""Tests for POST /activities/{activity_name}/signup endpoint."""
+
+
+def test_signup_successful(client):
+    """Test successful signup for an activity."""
+    # Arrange: Choose an existing activity and a new email
+    activity_name = "Chess Club"
+    email = "newstudent@mergington.edu"
+
+    # Act: Make POST request to signup endpoint
+    response = client.post(f"/activities/{activity_name}/signup?email={email}")
+
+    # Assert: Response status is 200
+    assert response.status_code == 200
+
+    # Assert: Response contains success message
+    result = response.json()
+    assert "message" in result
+    assert f"Signed up {email} for {activity_name}" in result["message"]
+
+    # Assert: Participant was added to the activity
+    activities_response = client.get("/activities")
+    activities = activities_response.json()
+    assert email in activities[activity_name]["participants"]
+
+
+def test_signup_non_existent_activity(client):
+    """Test signup for a non-existent activity returns 404."""
+    # Arrange: Use an invalid activity name
+    invalid_activity = "NonExistentActivity"
+    email = "student@mergington.edu"
+
+    # Act: Make POST request to signup endpoint
+    response = client.post(f"/activities/{invalid_activity}/signup?email={email}")
+
+    # Assert: Response status is 404
+    assert response.status_code == 404
+
+    # Assert: Response contains appropriate error message
+    result = response.json()
+    assert "detail" in result
+    assert "Activity not found" in result["detail"]
+
+
+def test_signup_duplicate_registration(client):
+    """Test that duplicate signup for same activity returns 400."""
+    # Arrange: First, sign up a student
+    activity_name = "Programming Class"
+    email = "duplicatestudent@mergington.edu"
+
+    # Sign up once (should succeed)
+    first_response = client.post(f"/activities/{activity_name}/signup?email={email}")
+    assert first_response.status_code == 200
+
+    # Act: Attempt to sign up the same student again
+    second_response = client.post(f"/activities/{activity_name}/signup?email={email}")
+
+    # Assert: Second signup returns 400
+    assert second_response.status_code == 400
+
+    # Assert: Response contains appropriate error message
+    result = second_response.json()
+    assert "detail" in result
+    assert "Student already signed up" in result["detail"]
\ No newline at end of file
diff --git a/tests/test_unregister.py b/tests/test_unregister.py
new file mode 100644
index 0000000..48a0832
--- /dev/null
+++ b/tests/test_unregister.py
@@ -0,0 +1,69 @@
+"""Tests for DELETE /activities/{activity_name}/participants/{email} endpoint."""
+
+
+def test_unregister_successful(client):
+    """Test successful unregister from an activity."""
+    # Arrange: First sign up a participant, then unregister them
+    activity_name = "Gym Class"
+    email = "tempstudent@mergington.edu"
+
+    # Sign up the participant
+    signup_response = client.post(f"/activities/{activity_name}/signup?email={email}")
+    assert signup_response.status_code == 200
+
+    # Verify they are signed up
+    activities_response = client.get("/activities")
+    activities = activities_response.json()
+    assert email in activities[activity_name]["participants"]
+
+    # Act: Make DELETE request to unregister endpoint
+    response = client.delete(f"/activities/{activity_name}/participants/{email}")
+
+    # Assert: Response status is 200
+    assert response.status_code == 200
+
+    # Assert: Response contains success message
+    result = response.json()
+    assert "message" in result
+    assert f"Unregistered {email} from {activity_name}" in result["message"]
+
+    # Assert: Participant was removed from the activity
+    activities_response = client.get("/activities")
+    activities = activities_response.json()
+    assert email not in activities[activity_name]["participants"]
+
+
+def test_unregister_non_existent_activity(client):
+    """Test unregister from a non-existent activity returns 404."""
+    # Arrange: Use an invalid activity name
+    invalid_activity = "NonExistentActivity"
+    email = "student@mergington.edu"
+
+    # Act: Make DELETE request to unregister endpoint
+    response = client.delete(f"/activities/{invalid_activity}/participants/{email}")
+
+    # Assert: Response status is 404
+    assert response.status_code == 404
+
+    # Assert: Response contains appropriate error message
+    result = response.json()
+    assert "detail" in result
+    assert "Activity not found" in result["detail"]
+
+
+def test_unregister_non_existent_participant(client):
+    """Test unregister of a participant not signed up returns 404."""
+    # Arrange: Use valid activity but email not registered
+    activity_name = "Tennis Club"
+    unregistered_email = "notsignedup@mergington.edu"
+
+    # Act: Make DELETE request to unregister endpoint
+    response = client.delete(f"/activities/{activity_name}/participants/{unregistered_email}")
+
+    # Assert: Response status is 404
+    assert response.status_code == 404
+
+    # Assert: Response contains appropriate error message
+    result = response.json()
+    assert "detail" in result
+    assert "Participant not found" in result["detail"]
\ No newline at end of file