diff --git a/tests/test.mp4 b/tests/test.mp4
new file mode 100644
index 0000000..995e692
Binary files /dev/null and b/tests/test.mp4 differ
diff --git a/tests/test_discord_embed.py b/tests/test_discord_embed.py
index 18adc93..9d6273a 100644
--- a/tests/test_discord_embed.py
+++ b/tests/test_discord_embed.py
@@ -1,4 +1,15 @@
+import imghdr
+import os
+
 from discord_embed import __version__, settings
+from discord_embed.generate_html import generate_html_for_videos
+from discord_embed.main import app
+from discord_embed.video import make_thumbnail, video_resolution
+from discord_embed.webhook import send_webhook
+from fastapi.testclient import TestClient
+
+client = TestClient(app)
+TEST_FILE = "tests/test.mp4"
 
 
 def test_version():
@@ -8,4 +19,108 @@ def test_version():
 
 def test_domain_ends_with_slash():
     """Test that domain ends with slash."""
-    assert not settings.domain.endswith("/")
+    assert not settings.serve_domain.endswith("/")
+
+
+def test_generate_html_for_videos():
+    """Test that generate_html_for_videos() works."""
+    # TODO: We should probably import this from settings.py instead of
+    # hardcoding it here. If we change it in settings.py, it won't be
+    # changed here.
+
+    domain = os.environ["SERVE_DOMAIN"]
+
+    # Remove trailing slash from domain
+    if domain.endswith("/"):
+        domain = domain[:-1]
+
+    generated_html = generate_html_for_videos(
+        url="https://www.youtube.com/watch?v=dQw4w9WgXcQ",
+        width=1920,
+        height=1080,
+        screenshot="https://i.ytimg.com/vi/dQw4w9WgXcQ/hqdefault.jpg",
+        filename="test_video.mp4",
+    )
+    assert generated_html == f"{domain}/test_video.mp4"
+
+
+def test_video_resolution():
+    """Test that video_resolution() works."""
+    assert video_resolution(TEST_FILE) == (422, 422)
+
+
+def test_make_thumbnail():
+    """Test that make_thumbnail() works."""
+    # TODO: We should probably import this from settings.py instead of
+    # hardcoding it here. If we change it in settings.py, it won't be
+    # changed here.
+
+    domain = os.environ["SERVE_DOMAIN"]
+
+    # Remove trailing slash from domain
+    if domain.endswith("/"):
+        domain = domain[:-1]
+
+    thumbnail = make_thumbnail(TEST_FILE, "test.mp4")
+    # Check that thumbnail is a jpeg.
+    assert imghdr.what(f"{settings.upload_folder}/test.mp4.jpg") == "jpeg"
+
+    # Check that the it returns the correct URL.
+    assert thumbnail == f"{domain}/test.mp4.jpg"
+
+
+def test_save_to_disk():
+    """Test that save_to_disk() works."""
+    # TODO: Implement this test. I need to mock the UploadFile object.
+
+
+def test_do_things():
+    """Test that do_things() works."""
+    # TODO: Implement this test. I need to mock the UploadFile object.
+
+
+def test_send_webhook():
+    """Test that send_webhook() works."""
+    send_webhook("Running Pytest")
+
+
+def test_main():
+    """Test that main() works."""
+    data_without_trailing_nl = ""
+    response = client.get("/")
+
+    # Check if response is our HTML.
+    with open("templates/index.html", encoding="utf8") as our_html:
+        data = our_html.read()
+
+        # index.html has a trailing newline that we need to remove.
+        if data[-1:] == "\n":
+            data_without_trailing_nl = data[:-1]
+
+    assert response.status_code == 200
+    assert response.text == data_without_trailing_nl
+
+
+def test_upload_file():
+    """Test if we can upload files."""
+    # TODO: We should probably import this from settings.py instead of
+    # hardcoding it here. If we change it in settings.py, it won't be
+    # changed here.
+
+    domain = os.environ["SERVE_DOMAIN"]
+
+    # Remove trailing slash from domain
+    if domain.endswith("/"):
+        domain = domain[:-1]
+
+    # Upload our video file and check if it returns the html_url.
+    with open(TEST_FILE, "rb") as uploaded_file:
+        response = client.post(
+            url="/uploadfiles/",
+            files={"file": uploaded_file},
+        )
+        returned_json = response.json()
+        html_url = returned_json["html_url"]
+
+    assert response.status_code == 200
+    assert html_url == f"{domain}/test.mp4"