diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..f73f0dd
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,39 @@
+# Python
+__pycache__/
+*.pyc
+*.pyo
+*.pyd
+*.db
+
+# Virtual environments
+.venv/
+venv/
+env/
+
+# Environment variables
+.env
+
+# Pytest
+.pytest_cache/
+
+# Logs
+*.log
+
+# VS Code
+.vscode/
+
+# OS files
+.DS_Store
+Thumbs.db
+
+# Node (frontend)
+node_modules/
+.next/
+dist/
+build/
+
+# uv
+.uv/
+
+# Misc
+*.sqlite3
\ No newline at end of file
diff --git a/backend/app/__init__.py b/backend/app/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/backend/app/pipeline/__init__.py b/backend/app/pipeline/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/backend/app/pipeline/utils.py b/backend/app/pipeline/utils.py
new file mode 100644
index 0000000..791cc0d
--- /dev/null
+++ b/backend/app/pipeline/utils.py
@@ -0,0 +1,36 @@
+from collections import defaultdict, deque
+
+def build_graph(pipeline):
+    graph = defaultdict(list)
+    in_degree = defaultdict(int)
+    
+    for node in pipeline["nodes"]:
+        node_id = node["id"]
+        graph[node_id] = []
+        in_degree[node_id] = 0
+        
+    for edge in pipeline["edges"]:
+        src = edge["source"]
+        dest = edge["target"]
+        if src not in graph or dest not in graph:
+            raise ValueError(f"Invalid edge: {src} -> {dest}")
+        graph[src].append(dest)
+        in_degree[dest] += 1
+        
+    return graph, in_degree
+
+def topological_sort(pipeline):
+    graph, in_degree = build_graph(pipeline)
+    queue = deque([node for node in in_degree if in_degree[node] == 0])
+    order = []
+    
+    while queue:
+        current = queue.popleft()
+        order.append(current)
+        for neighbor in graph[current]:
+            in_degree[neighbor] -= 1
+            if in_degree[neighbor] == 0:
+                queue.append(neighbor)
+    if len(order) != len(graph):
+        raise ValueError("Cycle detected in the pipeline")
+    return order
\ No newline at end of file
diff --git a/backend/pyproject.toml b/backend/pyproject.toml
index 4bab724..4d22a3f 100644
--- a/backend/pyproject.toml
+++ b/backend/pyproject.toml
@@ -9,6 +9,12 @@ dependencies = [
     "numpy>=2.4.4",
     "pandas>=3.0.2",
     "pydantic>=2.12.5",
+    "pytest>=9.0.2",
     "scikit-learn>=1.8.0",
     "uvicorn>=0.43.0",
 ]
+
+[dependency-groups]
+dev = [
+    "pytest>=9.0.2",
+]
diff --git a/backend/tests/__init__.py b/backend/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/backend/tests/test_utils.py b/backend/tests/test_utils.py
new file mode 100644
index 0000000..5a696cd
--- /dev/null
+++ b/backend/tests/test_utils.py
@@ -0,0 +1,51 @@
+from app.pipeline.utils import build_graph, topological_sort
+import pytest
+
+
+def test_build_graph():
+    pipeline = {
+        "nodes": [{"id": "A"}, {"id": "B"}],
+        "edges": [{"source": "A", "target": "B"}]
+    }
+
+    graph, in_degree = build_graph(pipeline)
+
+    assert dict(graph) == {"A": ["B"], "B": []}
+    assert dict(in_degree) == {"A": 0, "B": 1}
+
+
+def test_topological_sort():
+    pipeline = {
+        "nodes": [{"id": "A"}, {"id": "B"}, {"id": "C"}],
+        "edges": [
+            {"source": "A", "target": "B"},
+            {"source": "B", "target": "C"}
+        ]
+    }
+
+    order = topological_sort(pipeline)
+
+    assert order == ["A", "B", "C"]
+
+
+def test_cycle_detection():
+    pipeline = {
+        "nodes": [{"id": "A"}, {"id": "B"}],
+        "edges": [
+            {"source": "A", "target": "B"},
+            {"source": "B", "target": "A"}
+        ]
+    }
+
+    with pytest.raises(ValueError):
+        topological_sort(pipeline)
+
+
+def test_invalid_edge():
+    pipeline = {
+        "nodes": [{"id": "A"}],
+        "edges": [{"source": "A", "target": "X"}]
+    }
+
+    with pytest.raises(ValueError):
+        build_graph(pipeline)
\ No newline at end of file
diff --git a/backend/uv.lock b/backend/uv.lock
index 274c5eb..d053327 100644
--- a/backend/uv.lock
+++ b/backend/uv.lock
@@ -46,20 +46,30 @@ dependencies = [
     { name = "numpy" },
     { name = "pandas" },
     { name = "pydantic" },
+    { name = "pytest" },
     { name = "scikit-learn" },
     { name = "uvicorn" },
 ]
 
+[package.dev-dependencies]
+dev = [
+    { name = "pytest" },
+]
+
 [package.metadata]
 requires-dist = [
     { name = "fastapi", specifier = ">=0.135.3" },
     { name = "numpy", specifier = ">=2.4.4" },
     { name = "pandas", specifier = ">=3.0.2" },
     { name = "pydantic", specifier = ">=2.12.5" },
+    { name = "pytest", specifier = ">=9.0.2" },
     { name = "scikit-learn", specifier = ">=1.8.0" },
     { name = "uvicorn", specifier = ">=0.43.0" },
 ]
 
+[package.metadata.requires-dev]
+dev = [{ name = "pytest", specifier = ">=9.0.2" }]
+
 [[package]]
 name = "click"
 version = "8.3.2"
@@ -115,6 +125,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/0e/61/66938bbb5fc52dbdf84594873d5b51fb1f7c7794e9c0f5bd885f30bc507b/idna-3.11-py3-none-any.whl", hash = "sha256:771a87f49d9defaf64091e6e6fe9c18d4833f140bd19464795bc32d966ca37ea", size = 71008, upload-time = "2025-10-12T14:55:18.883Z" },
 ]
 
+[[package]]
+name = "iniconfig"
+version = "2.3.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/72/34/14ca021ce8e5dfedc35312d08ba8bf51fdd999c576889fc2c24cb97f4f10/iniconfig-2.3.0.tar.gz", hash = "sha256:c76315c77db068650d49c5b56314774a7804df16fee4402c1f19d6d15d8c4730", size = 20503, upload-time = "2025-10-18T21:55:43.219Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/cb/b1/3846dd7f199d53cb17f49cba7e651e9ce294d8497c8c150530ed11865bb8/iniconfig-2.3.0-py3-none-any.whl", hash = "sha256:f631c04d2c48c52b84d0d0549c99ff3859c98df65b3101406327ecc7d53fbf12", size = 7484, upload-time = "2025-10-18T21:55:41.639Z" },
+]
+
 [[package]]
 name = "joblib"
 version = "1.5.3"
@@ -153,6 +172,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/58/78/548fb8e07b1a341746bfbecb32f2c268470f45fa028aacdbd10d9bc73aab/numpy-2.4.4-cp314-cp314t-win_arm64.whl", hash = "sha256:ba203255017337d39f89bdd58417f03c4426f12beed0440cfd933cb15f8669c7", size = 10566643, upload-time = "2026-03-29T13:21:34.339Z" },
 ]
 
+[[package]]
+name = "packaging"
+version = "26.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/65/ee/299d360cdc32edc7d2cf530f3accf79c4fca01e96ffc950d8a52213bd8e4/packaging-26.0.tar.gz", hash = "sha256:00243ae351a257117b6a241061796684b084ed1c516a08c48a3f7e147a9d80b4", size = 143416, upload-time = "2026-01-21T20:50:39.064Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/b7/b9/c538f279a4e237a006a2c98387d081e9eb060d203d8ed34467cc0f0b9b53/packaging-26.0-py3-none-any.whl", hash = "sha256:b36f1fef9334a5588b4166f8bcd26a14e521f2b55e6b9de3aaa80d3ff7a37529", size = 74366, upload-time = "2026-01-21T20:50:37.788Z" },
+]
+
 [[package]]
 name = "pandas"
 version = "3.0.2"
@@ -182,6 +210,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/cb/2b/f8434233fab2bd66a02ec014febe4e5adced20e2693e0e90a07d118ed30e/pandas-3.0.2-cp314-cp314t-win_arm64.whl", hash = "sha256:5371b72c2d4d415d08765f32d689217a43227484e81b2305b52076e328f6f482", size = 9455341, upload-time = "2026-03-31T06:48:28.418Z" },
 ]
 
+[[package]]
+name = "pluggy"
+version = "1.6.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/f9/e2/3e91f31a7d2b083fe6ef3fa267035b518369d9511ffab804f839851d2779/pluggy-1.6.0.tar.gz", hash = "sha256:7dcc130b76258d33b90f61b658791dede3486c3e6bfb003ee5c9bfb396dd22f3", size = 69412, upload-time = "2025-05-15T12:30:07.975Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/54/20/4d324d65cc6d9205fabedc306948156824eb9f0ee1633355a8f7ec5c66bf/pluggy-1.6.0-py3-none-any.whl", hash = "sha256:e920276dd6813095e9377c0bc5566d94c932c33b27a3e3945d8389c374dd4746", size = 20538, upload-time = "2025-05-15T12:30:06.134Z" },
+]
+
 [[package]]
 name = "pydantic"
 version = "2.12.5"
@@ -236,6 +273,31 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/9f/ed/068e41660b832bb0b1aa5b58011dea2a3fe0ba7861ff38c4d4904c1c1a99/pydantic_core-2.41.5-cp314-cp314t-win_arm64.whl", hash = "sha256:35b44f37a3199f771c3eaa53051bc8a70cd7b54f333531c59e29fd4db5d15008", size = 1974769, upload-time = "2025-11-04T13:42:01.186Z" },
 ]
 
+[[package]]
+name = "pygments"
+version = "2.20.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/c3/b2/bc9c9196916376152d655522fdcebac55e66de6603a76a02bca1b6414f6c/pygments-2.20.0.tar.gz", hash = "sha256:6757cd03768053ff99f3039c1a36d6c0aa0b263438fcab17520b30a303a82b5f", size = 4955991, upload-time = "2026-03-29T13:29:33.898Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/f4/7e/a72dd26f3b0f4f2bf1dd8923c85f7ceb43172af56d63c7383eb62b332364/pygments-2.20.0-py3-none-any.whl", hash = "sha256:81a9e26dd42fd28a23a2d169d86d7ac03b46e2f8b59ed4698fb4785f946d0176", size = 1231151, upload-time = "2026-03-29T13:29:30.038Z" },
+]
+
+[[package]]
+name = "pytest"
+version = "9.0.2"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "colorama", marker = "sys_platform == 'win32'" },
+    { name = "iniconfig" },
+    { name = "packaging" },
+    { name = "pluggy" },
+    { name = "pygments" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/d1/db/7ef3487e0fb0049ddb5ce41d3a49c235bf9ad299b6a25d5780a89f19230f/pytest-9.0.2.tar.gz", hash = "sha256:75186651a92bd89611d1d9fc20f0b4345fd827c41ccd5c299a868a05d70edf11", size = 1568901, upload-time = "2025-12-06T21:30:51.014Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/3b/ab/b3226f0bd7cdcf710fbede2b3548584366da3b19b5021e74f5bde2a8fa3f/pytest-9.0.2-py3-none-any.whl", hash = "sha256:711ffd45bf766d5264d487b917733b453d917afd2b0ad65223959f59089f875b", size = 374801, upload-time = "2025-12-06T21:30:49.154Z" },
+]
+
 [[package]]
 name = "python-dateutil"
 version = "2.9.0.post0"