From 891f79ef8c78e112b087f0284e397de18fe3494f Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 3 Jun 2026 23:23:40 +0000
Subject: [PATCH 1/9] Initial plan


From 27165cf4d0d4b8e9466d776b57ce4e1a9c537682 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 3 Jun 2026 23:25:31 +0000
Subject: [PATCH 2/9] Update devcontainer for Codespaces Docker workflow

---
 .devcontainer/devcontainer.json | 6 ++++--
 README.md                       | 5 +++--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index 14a6eb7..0c88853 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -1,7 +1,7 @@
 {
 	"name": "MLE Interview",
 	// Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
-	"image": "mcr.microsoft.com/devcontainers/python:1-3.10",
+	"image": "mcr.microsoft.com/devcontainers/python:1-3.10-bookworm",
 	"customizations": {
 		"vscode": {
 			"settings": {
@@ -18,9 +18,11 @@
 			},
 			"extensions": [
 				"charliermarsh.ruff",
+				"github.codespaces",
 				"ms-azuretools.vscode-docker",
 				"ms-python.black-formatter",
 				"ms-python.python",
+				"ms-vscode-remote.remote-containers",
 				"ms-toolsai.jupyter",
 				"redhat.vscode-yaml",
 				"vscode-icons-team.vscode-icons",
@@ -29,7 +31,7 @@
 		}
 	},
 	"features": {
-		"ghcr.io/devcontainers/features/docker-in-docker": {}
+		"ghcr.io/devcontainers/features/docker-in-docker:2": {}
 	},
 	"postCreateCommand": "make setup"
 }
\ No newline at end of file
diff --git a/README.md b/README.md
index 5306772..c8dd6b1 100644
--- a/README.md
+++ b/README.md
@@ -4,12 +4,13 @@
 ## Setup
 1. Install [Visual Studio Code](https://code.visualstudio.com/). Also the following plugins:
     - [Dev Containers](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers)
+    - [GitHub Codespaces](https://marketplace.visualstudio.com/items?itemName=GitHub.codespaces)
 2. Clone this repo
 3. Open the repository in VSCode (`code .`)
 4. VSCode will prompt you to install recommended extensions. Select `Yes`
     - If you missed this step, you can install recommended extensions using the extensions sidebar (`⇧⌘X`)
 5. VSCode will prompt you to reopen the workspace in a Dev Container. Select `Yes`.
-    - If you missed this step, open the command prompt palette (`⇧⌘P`) and run the command `Remote-Containers: Rebuild and Reopen in Container`
+    - If you missed this step, open the command prompt palette (`⇧⌘P`) and run the command `Dev Containers: Rebuild and Reopen in Container`
 
 
 ## Make Commands
@@ -20,7 +21,7 @@ Before you start, ensure you have all the necessary dependencies installed:
 make setup
 ```
 
-This command will install the Python dependencies listed in `requirements.txt`. 
+This command will install the Python dependencies listed in `requirements.txt`. The project is configured to run in the Dev Container's Python 3.10 environment for TensorFlow compatibility.
 
 ### Serve API
 

From 29d62b8b856076cac8f39c82b073c02cf5d8c614 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 3 Jun 2026 23:26:12 +0000
Subject: [PATCH 3/9] Refine devcontainer setup docs

---
 README.md | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index c8dd6b1..48e8673 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@
 ## Setup
 1. Install [Visual Studio Code](https://code.visualstudio.com/). Also the following plugins:
     - [Dev Containers](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers)
-    - [GitHub Codespaces](https://marketplace.visualstudio.com/items?itemName=GitHub.codespaces)
+    - (Optional for local development) [GitHub Codespaces](https://marketplace.visualstudio.com/items?itemName=GitHub.codespaces)
 2. Clone this repo
 3. Open the repository in VSCode (`code .`)
 4. VSCode will prompt you to install recommended extensions. Select `Yes`
@@ -21,7 +21,8 @@ Before you start, ensure you have all the necessary dependencies installed:
 make setup
 ```
 
-This command will install the Python dependencies listed in `requirements.txt`. The project is configured to run in the Dev Container's Python 3.10 environment for TensorFlow compatibility.
+This command will install the Python dependencies listed in `requirements.txt`.
+The project is configured to run in the Dev Container's Python 3.10 environment for TensorFlow compatibility.
 
 ### Serve API
 

From 9e9a7c347e0955861073b9eebc04eb22d34dac35 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 3 Jun 2026 23:26:43 +0000
Subject: [PATCH 4/9] Remove host-only extensions from container config

---
 .devcontainer/devcontainer.json | 2 --
 1 file changed, 2 deletions(-)

diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index 0c88853..c337483 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -18,11 +18,9 @@
 			},
 			"extensions": [
 				"charliermarsh.ruff",
-				"github.codespaces",
 				"ms-azuretools.vscode-docker",
 				"ms-python.black-formatter",
 				"ms-python.python",
-				"ms-vscode-remote.remote-containers",
 				"ms-toolsai.jupyter",
 				"redhat.vscode-yaml",
 				"vscode-icons-team.vscode-icons",

From d5e69f934047f948a439b5f0b16d6e9354bab2ec Mon Sep 17 00:00:00 2001
From: Edgar Pino <edgar-pino@pluralsight.com>
Date: Wed, 3 Jun 2026 21:20:12 -0500
Subject: [PATCH 5/9] Update devcontainer configuration for Python 3.12 and
 Docker-in-Docker feature

---
 .devcontainer/devcontainer-lock.json | 9 +++++++++
 .devcontainer/devcontainer.json      | 6 ++++--
 2 files changed, 13 insertions(+), 2 deletions(-)
 create mode 100644 .devcontainer/devcontainer-lock.json

diff --git a/.devcontainer/devcontainer-lock.json b/.devcontainer/devcontainer-lock.json
new file mode 100644
index 0000000..fbc79c1
--- /dev/null
+++ b/.devcontainer/devcontainer-lock.json
@@ -0,0 +1,9 @@
+{
+  "features": {
+    "ghcr.io/devcontainers/features/docker-in-docker:3": {
+      "version": "3.0.1",
+      "resolved": "ghcr.io/devcontainers/features/docker-in-docker@sha256:ca2508495b01ba29eba93e8153772a2daa65eaa86471cc6863fe2a3d21933df9",
+      "integrity": "sha256:ca2508495b01ba29eba93e8153772a2daa65eaa86471cc6863fe2a3d21933df9"
+    }
+  }
+}
diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index c337483..ed24b11 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -1,7 +1,7 @@
 {
 	"name": "MLE Interview",
 	// Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
-	"image": "mcr.microsoft.com/devcontainers/python:1-3.10-bookworm",
+	"image": "mcr.microsoft.com/devcontainers/python:3.12",
 	"customizations": {
 		"vscode": {
 			"settings": {
@@ -29,7 +29,9 @@
 		}
 	},
 	"features": {
-		"ghcr.io/devcontainers/features/docker-in-docker:2": {}
+		"ghcr.io/devcontainers/features/docker-in-docker:3": {
+			"moby": false
+		}
 	},
 	"postCreateCommand": "make setup"
 }
\ No newline at end of file

From 11edee435e1c0c1e3cd0f5373fa58b0260cd9cbf Mon Sep 17 00:00:00 2001
From: Edgar Pino <edgar-pino@pluralsight.com>
Date: Wed, 3 Jun 2026 22:06:56 -0500
Subject: [PATCH 6/9] Add Dockerfile and update devcontainer configuration for
 Zscaler integration

---
 .devcontainer/Dockerfile        |  9 +++++++++
 .devcontainer/devcontainer.json | 11 ++++++-----
 .gitignore                      |  3 +++
 INTERVIEW.md                    |  3 +--
 4 files changed, 19 insertions(+), 7 deletions(-)
 create mode 100644 .devcontainer/Dockerfile

diff --git a/.devcontainer/Dockerfile b/.devcontainer/Dockerfile
new file mode 100644
index 0000000..fe5f950
--- /dev/null
+++ b/.devcontainer/Dockerfile
@@ -0,0 +1,9 @@
+FROM mcr.microsoft.com/devcontainers/python:3.10
+
+COPY zscaler-bundle.pem /tmp/zscaler.pem
+RUN if [ -s /tmp/zscaler.pem ]; then \
+      cp /tmp/zscaler.pem /usr/local/share/ca-certificates/zscaler.crt && \
+      update-ca-certificates; \
+    fi && rm -f /tmp/zscaler.pem
+
+RUN find /etc/apt /usr/share/keyrings -name "*yarn*" -delete 2>/dev/null || true
diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index ed24b11..4de17f2 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -1,7 +1,7 @@
 {
 	"name": "MLE Interview",
-	// Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
-	"image": "mcr.microsoft.com/devcontainers/python:3.12",
+	"build": { "dockerfile": "Dockerfile" },
+	"initializeCommand": "cp ~/.ssl/zscaler-bundle.pem .devcontainer/zscaler-bundle.pem 2>/dev/null || touch .devcontainer/zscaler-bundle.pem",
 	"customizations": {
 		"vscode": {
 			"settings": {
@@ -14,7 +14,7 @@
 						"source.organizeImports.ruff": true,
 						"source.organizeImports": true
 					}
-				},
+				}
 			},
 			"extensions": [
 				"charliermarsh.ruff",
@@ -30,8 +30,9 @@
 	},
 	"features": {
 		"ghcr.io/devcontainers/features/docker-in-docker:3": {
-			"moby": false
+			"moby": false,
+			"disableIp6tables": true
 		}
 	},
 	"postCreateCommand": "make setup"
-}
\ No newline at end of file
+}
diff --git a/.gitignore b/.gitignore
index 3f83ee9..8d5a0af 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,6 @@
+# Zscaler cert (machine-specific, copied by initializeCommand)
+.devcontainer/zscaler-bundle.pem
+
 # Byte-compiled / optimized / DLL files
 __pycache__/
 *.py[cod]
diff --git a/INTERVIEW.md b/INTERVIEW.md
index 534694b..46e3333 100644
--- a/INTERVIEW.md
+++ b/INTERVIEW.md
@@ -1,8 +1,7 @@
 
 ## Coding Challenge
 
-You can refer to Google or relevant documentation to guide you in addressing the issues below. 
-You are not allowed to use ChatGPT, Copilot, or any similar tools for assistance. 
+You can refer to Google or relevant documentation to guide you in addressing the issues below.  
 
 1. **Model Training Error Resolution:**
    - Begin by executing `make test` to identify any issues during model training.

From 91f3646457ffeb7d8d1486c8e5138edae44ac80a Mon Sep 17 00:00:00 2001
From: Edgar Pino <edgar-pino@pluralsight.com>
Date: Wed, 3 Jun 2026 22:16:00 -0500
Subject: [PATCH 7/9] Enhance interview documentation and Makefile with
 detailed task instructions and API features

---
 INTERVIEW.md | 119 +++++++++++++++++++++++++++++++++++++++++++--------
 Makefile     |   3 ++
 README.md    | 118 +++++++++++++++++++-------------------------------
 3 files changed, 147 insertions(+), 93 deletions(-)

diff --git a/INTERVIEW.md b/INTERVIEW.md
index 46e3333..39bca5b 100644
--- a/INTERVIEW.md
+++ b/INTERVIEW.md
@@ -1,27 +1,108 @@
-
 ## Coding Challenge
 
-You can refer to Google or relevant documentation to guide you in addressing the issues below.  
+You are working on a user interest recommendation system. It consists of:
+
+- A **TensorFlow model** trained on user content interactions, served via TF Serving (Docker)
+- A **Flask API** that fetches user features, calls the model, and returns ranked interests
+- A **feature store** backed by CSV files
+
+There are **6 tasks** to complete. Tasks 1–5 each have a failing test that tells you exactly what to fix. Task 6 is an open-ended feature implementation. You can refer to Google or relevant documentation — no AI-assisted coding tools.
+
+---
+
+### Terminal setup (do this before task 3)
+
+Once the model is trained and served, you'll need **two terminals** running simultaneously inside the container:
+
+| Terminal | Command | Purpose |
+|---|---|---|
+| 1 | `make serve-model` | TF Serving on port 8501 |
+| 2 | `make serve-api` | Flask API on port 5005 |
+
+Keep both running while working on tasks 3–6.
+
+---
+
+### Tasks
+
+**1. Fix model training**
+
+Run `make test`. The `TestModel::test_model_build` test fails.
+
+Find and fix the bug in the model code, then verify:
+```
+make test  # TestModel::test_model_build must pass
+```
+
+Once passing, train the model and start the model server (leave it running):
+```
+make train
+make serve-model
+```
+
+---
+
+**2. Fix the API startup**
+
+Run `make serve-api`. The Flask application fails to start.
+
+Find and fix the bug, then verify the server starts without errors:
+```
+make serve-api
+```
+
+Leave the server running in its terminal.
+
+---
+
+**3. Fix the interests count**
+
+With both servers running, run `make test`. This test fails:
+```
+TestInterestsAPI::test_basic_response — AssertionError: Incorrect number of interests
+```
+
+Fix the API so it returns the correct number of interests. Verify:
+```
+make test  # test_basic_response must pass (interests count assertion)
+```
+
+---
+
+**4. Fix response time**
+
+With both servers running, run `make test`. This test fails:
+```
+TestInterestsAPI::test_basic_response — AssertionError: Request greater than 1 second
+```
+
+Find the performance bottleneck and fix it. Verify:
+```
+make test  # test_basic_response must pass (timing assertion)
+```
+
+---
+
+**5. Add probability to the response**
+
+With both servers running, run `make test`. This test fails:
+```
+TestInterestsAPI::test_with_probability_threshold
+```
 
-1. **Model Training Error Resolution:**
-   - Begin by executing `make test` to identify any issues during model training.
-   - After passing the `TestModel::test_model_build` test, use `make train` followed by `make serve-model` to train and serve the model, preparing it for upcoming steps.
+Update the API response so each interest includes a `probability` field. Verify:
+```
+make test  # test_with_probability_threshold must pass
+```
 
-2. **API Startup Issue Fix:**
-   - Resolve the Flask API startup issue with `make serve-api`.
-   - Run `make serve-api` to start a development Flask server, then open a new terminal window without shutting down the server.
+---
 
-3. **Data Return and Interests Length Correction:**
-   - Execute `make test` and resolve the `TestInterestsAPI::test_basic_response - AssertionError: Incorrect number of interests` test.
-   - Ensure the return data structure and interests array length meet the specifications, adjusting the API as necessary.
+**6. Add probability threshold filtering**
 
-4. **Response Time Optimization:**
-   - Run `make test` and fix the `TestInterestsAPI::test_basic_response - AssertionError: Request greater than 1 second` test.
-   - Enhance the API to achieve a response time of one second or less.
+Implement a feature that lets API clients filter results by a minimum probability score. For example:
 
-5. **Probability Field Inclusion:**
-   - Perform `make test` and correct the `TestInterestsAPI::test_with_probability` test.
-   - Update the API response to incorporate a 'probability' field.
+```
+GET /interests/<user_handle>?min_probability=0.5
+```
 
-6. **Probability Score Filtering Implementation:**
-   - Create a feature allowing API clients to filter results by probability score, enabling users to specify a probability threshold for more targeted results.
\ No newline at end of file
+Should return only interests with probability ≥ 0.5. There is no automated test for this task — demonstrate it works with a curl request.
diff --git a/Makefile b/Makefile
index 80daa2d..9468596 100644
--- a/Makefile
+++ b/Makefile
@@ -7,6 +7,9 @@ serve-api:
 serve-model:
 	docker compose up tf-serving
 
+ping-model:
+	curl -s http://localhost:8501/v1/models/interests-model | python3 -m json.tool
+
 train:
 	TF_CPP_MIN_LOG_LEVEL=3 python -m model.main
 
diff --git a/README.md b/README.md
index 48e8673..c709418 100644
--- a/README.md
+++ b/README.md
@@ -1,122 +1,92 @@
-# MLE Interview:
-
+# MLE Interview
 
 ## Setup
-1. Install [Visual Studio Code](https://code.visualstudio.com/). Also the following plugins:
-    - [Dev Containers](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers)
-    - (Optional for local development) [GitHub Codespaces](https://marketplace.visualstudio.com/items?itemName=GitHub.codespaces)
-2. Clone this repo
-3. Open the repository in VSCode (`code .`)
-4. VSCode will prompt you to install recommended extensions. Select `Yes`
-    - If you missed this step, you can install recommended extensions using the extensions sidebar (`⇧⌘X`)
-5. VSCode will prompt you to reopen the workspace in a Dev Container. Select `Yes`.
-    - If you missed this step, open the command prompt palette (`⇧⌘P`) and run the command `Dev Containers: Rebuild and Reopen in Container`
+
+### Option A — GitHub Codespaces (recommended)
+
+Click **Code → Open with Codespaces** on the repository page. The environment builds automatically — no local installation needed.
+
+### Option B — Local Dev Container (VS Code)
+
+1. Install [Visual Studio Code](https://code.visualstudio.com/) and the [Dev Containers](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers) extension
+2. Install [Docker Desktop](https://www.docker.com/products/docker-desktop/)
+3. Clone this repo and open it in VS Code (`code .`)
+4. VS Code will prompt you to reopen in a Dev Container — select **Yes**
+   - If you miss the prompt: `⇧⌘P` → **Dev Containers: Rebuild and Reopen in Container**
+
+> **Note (corporate networks / Zscaler):** If your machine uses Zscaler SSL inspection, ensure your Zscaler certificate bundle exists at `~/.ssl/zscaler-bundle.pem` before building the container. The build handles this automatically.
+
+Once the container starts, dependencies are installed automatically via `make setup`. You do not need to run it manually.
 
 
 ## Make Commands
 
-Before you start, ensure you have all the necessary dependencies installed:
+### Test
 
 ```
-make setup
+make test
 ```
 
-This command will install the Python dependencies listed in `requirements.txt`.
-The project is configured to run in the Dev Container's Python 3.10 environment for TensorFlow compatibility.
+Runs all tests in `./tests` with pytest. Use this to verify each task as you work through the interview.
 
-### Serve API
-
-To start the Flask API, use the following command:
+### Train
 
 ```
-make serve-api
+make train
 ```
 
-This command launches the Flask application defined in `api/app` on port 5005, accessible via `0.0.0.0`. The `--debug` flag is included to enable debug mode, which provides useful debugging information in case of errors and automatically reloads the server on code changes.
+Trains the model using `model/main.py` and exports a SavedModel to `serving/interests-model/1/`.
 
 ### Serve Model
 
-If you're using a TensorFlow model served via Docker, you can start the TensorFlow serving using:
-
 ```
 make serve-model
 ```
 
-This command uses Docker Compose to spin up a container defined in the Docker configuration, specifically targeting the TensorFlow serving service (`tf-serving`). Ensure Docker is installed and running on your system before executing this command.
+Starts TF Serving via Docker Compose on port 8501. Run this after `make train` — the model must be trained first.
 
-### Train
-
-To train the model, execute:
+### Serve API
 
 ```
-make train
+make serve-api
 ```
 
-This command runs the main training script located at `model.main`. 
+Starts the Flask development server on port 5005. Requires the model server to be running for inference endpoints to work.
 
-### Test
 
-Finally, to run the tests for your project, use:
+## API
 
 ```
-make test
+GET http://localhost:5005/interests/<user_handle>
 ```
 
-This command runs all the tests in the `./tests` directory using pytest. 
+Optional query parameters:
+- `top_k` (int) — number of interests to return (default: 10)
+- `min_probability` (float) — filter results below this probability score
 
+Example response:
 
-## API
-
-Route: GET: http://localhost:5005/interests/:userHandle
-
-API Response:
-
-```
+```json
 {
     "user_handle": "e337a675-46f5-437e-aa72-5d43643b5461",
+    "name": "Kisiza",
+    "type": "B2B",
     "interests": [
         {
             "id": "29e020bb-7a02-41db-b21f-527a8ef4dfdf",
-            "label": "Accounting technician"
+            "label": "Accounting technician",
+            "probability": 0.94
         },
         {
             "id": "012abcd1-3a6a-4803-a47e-42f46b402024",
-            "label": "Field seismologist"
+            "label": "Field seismologist",
+            "probability": 0.87
         },
         {
             "id": "a1b028dd-8464-4c63-85e8-ae29ea184fc7",
-            "label": "Designer, industrial/product"
-        },
-        {
-            "id": "686af7e4-6d58-4148-b227-3bf65ff10273",
-            "label": "Materials engineer"
-        },
-        {
-            "id": "8d1526b9-a7bf-4972-be43-7b912f149667",
-            "label": "Fashion designer"
-        },
-        {
-            "id": "d83a55a3-0143-4318-91c1-88f44ad59390",
-            "label": "Journalist, newspaper"
-        },
-        {
-            "id": "cda4441f-dba6-495c-9e2e-7429bd5e0465",
-            "label": "Therapist, music"
-        },
-        {
-            "id": "e9b23ad4-753b-4331-9cfa-525965fcf281",
-            "label": "Secretary, company"
-        },
-        {
-            "id": "ca4b03b2-0ae2-440a-afc8-5469510b19cb",
-            "label": "Commissioning editor"
-        },
-        {
-            "id": "fd3c41b8-8c15-47e2-a80d-cf3683b2d0da",
-            "label": "Copywriter, advertising"
+            "label": "Designer, industrial/product",
+            "probability": 0.81
         }
-    ],
-    "name": "Kisiza",
-    "type": "B2B"
+    ]
 }
-```
\ No newline at end of file
+```

From c7e9f85bbef0d522c65ef3c56b99428ac03fc088 Mon Sep 17 00:00:00 2001
From: Edgar Pino <edgar-pino@pluralsight.com>
Date: Thu, 4 Jun 2026 03:48:57 +0000
Subject: [PATCH 8/9] Update interview tasks and add probability score
 validation in tests

---
 INTERVIEW.md        | 27 ++++++++++++++++++++-------
 tests/test_model.py | 15 +++++++++++++++
 2 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/INTERVIEW.md b/INTERVIEW.md
index 39bca5b..93360e8 100644
--- a/INTERVIEW.md
+++ b/INTERVIEW.md
@@ -6,11 +6,11 @@ You are working on a user interest recommendation system. It consists of:
 - A **Flask API** that fetches user features, calls the model, and returns ranked interests
 - A **feature store** backed by CSV files
 
-There are **6 tasks** to complete. Tasks 1–5 each have a failing test that tells you exactly what to fix. Task 6 is an open-ended feature implementation. You can refer to Google or relevant documentation — no AI-assisted coding tools.
+There are **7 tasks** to complete. Tasks 1–6 each have a failing test or a clear broken behaviour that tells you what to fix. Task 7 is an open-ended feature implementation. You can refer to Google or relevant documentation — no AI-assisted coding tools.
 
 ---
 
-### Terminal setup (do this before task 3)
+### Terminal setup (do this before task 4)
 
 Once the model is trained and served, you'll need **two terminals** running simultaneously inside the container:
 
@@ -19,7 +19,7 @@ Once the model is trained and served, you'll need **two terminals** running simu
 | 1 | `make serve-model` | TF Serving on port 8501 |
 | 2 | `make serve-api` | Flask API on port 5005 |
 
-Keep both running while working on tasks 3–6.
+Keep both running while working on tasks 4–7.
 
 ---
 
@@ -55,7 +55,20 @@ Leave the server running in its terminal.
 
 ---
 
-**3. Fix the interests count**
+**3. Fix the probability scores**
+
+The model's serving function returns raw logit scores, not probabilities. These values are not bounded between 0 and 1 and cannot be meaningfully compared or filtered.
+
+Find where the issue originates and fix it so that the scores returned represent proper probability values. There are two valid approaches — both are acceptable.
+
+Verify:
+```
+make test  # TestModel::test_probability_scores must pass
+```
+
+---
+
+**4. Fix the interests count**
 
 With both servers running, run `make test`. This test fails:
 ```
@@ -69,7 +82,7 @@ make test  # test_basic_response must pass (interests count assertion)
 
 ---
 
-**4. Fix response time**
+**5. Fix response time**
 
 With both servers running, run `make test`. This test fails:
 ```
@@ -83,7 +96,7 @@ make test  # test_basic_response must pass (timing assertion)
 
 ---
 
-**5. Add probability to the response**
+**6. Add probability to the response**
 
 With both servers running, run `make test`. This test fails:
 ```
@@ -97,7 +110,7 @@ make test  # test_with_probability_threshold must pass
 
 ---
 
-**6. Add probability threshold filtering**
+**7. Add probability threshold filtering**
 
 Implement a feature that lets API clients filter results by a minimum probability score. For example:
 
diff --git a/tests/test_model.py b/tests/test_model.py
index 5469061..541552c 100644
--- a/tests/test_model.py
+++ b/tests/test_model.py
@@ -32,6 +32,21 @@ def setup_method(self):
             hyper_params=hyper_params,
         )
 
+    def test_probability_scores(self):
+        input_record = {
+            "USER_HANDLE": tf.constant([self.users[0]]),
+            "USER_TYPE": tf.constant(["B2B"]),
+            "CONTENT_TITLES_JOINED": tf.constant([self.content_titles[0]]),
+        }
+        top_k = tf.constant(1, dtype=tf.int64)
+
+        result = self.model.serving_predict(input_record, top_k)
+        probabilities = result["probabilities"].numpy().flatten()
+
+        assert all(0 <= p <= 1 for p in probabilities), (
+            "Probabilities must be between 0 and 1"
+        )
+
     def test_model_build(self):
         interests_input = [self.interests_vocab[0], self.interests_vocab[3]]
 

From 33bd68798d9c6670572195559f4979202179580a Mon Sep 17 00:00:00 2001
From: Edgar Pino <edgar-pino@pluralsight.com>
Date: Tue, 15 Sep 2026 14:42:59 -0500
Subject: [PATCH 9/9] Refactor interview tasks and update testing instructions
 in documentation and Makefile

---
 INTERVIEW.md      | 66 +++++++++++++++++++++++++++++++++++------------
 Makefile          | 53 +++++++++++++++++++++++++++++++++++--
 README.md         | 16 +++++++++++-
 pytest.ini        |  3 +++
 tests/conftest.py | 31 ++++++++++++++++++++++
 tests/test_app.py | 36 ++++++++++++++++++++------
 6 files changed, 177 insertions(+), 28 deletions(-)
 create mode 100644 pytest.ini
 create mode 100644 tests/conftest.py

diff --git a/INTERVIEW.md b/INTERVIEW.md
index 93360e8..b14ecdc 100644
--- a/INTERVIEW.md
+++ b/INTERVIEW.md
@@ -6,7 +6,29 @@ You are working on a user interest recommendation system. It consists of:
 - A **Flask API** that fetches user features, calls the model, and returns ranked interests
 - A **feature store** backed by CSV files
 
-There are **7 tasks** to complete. Tasks 1–6 each have a failing test or a clear broken behaviour that tells you what to fix. Task 7 is an open-ended feature implementation. You can refer to Google or relevant documentation — no AI-assisted coding tools.
+There are **7 tasks** to complete. Tasks 1, 3, 4, 5 and 6 each have a failing test that tells you what to fix. Tasks 2 and 7 are verified by running the app. You can refer to Google or relevant documentation — no AI-assisted coding tools.
+
+---
+
+### Running the tests
+
+**Every task has its own command** — `make test-1` through `make test-7`. Run only the one for the task you are on:
+
+```
+make test-4
+```
+
+`make test` runs everything at once. Avoid it until the end: tests for tasks you have not reached yet will fail and bury the output you care about.
+
+**Read the last few lines of the output.** Each test failure ends with the assertion message that names exactly what is wrong, for example:
+
+```
+E   AssertionError: Incorrect number of interests
+```
+
+That message is the whole signal — you do not need to read the traceback above it.
+
+**The tests are correct.** Nearly every fix belongs in the source code, in `api/` or `model/` — not in `tests/`. **Task 4 is the only exception:** `top_k` has to be passed into the request as a query parameter, so that test does change.
 
 ---
 
@@ -27,11 +49,11 @@ Keep both running while working on tasks 4–7.
 
 **1. Fix model training**
 
-Run `make test`. The `TestModel::test_model_build` test fails.
+Run `make test-1`. The test fails.
 
 Find and fix the bug in the model code, then verify:
 ```
-make test  # TestModel::test_model_build must pass
+make test-1
 ```
 
 Once passing, train the model and start the model server (leave it running):
@@ -46,12 +68,15 @@ make serve-model
 
 Run `make serve-api`. The Flask application fails to start.
 
-Find and fix the bug, then verify the server starts without errors:
+Find and fix the bug, then start the server again and leave it running in its terminal:
 ```
 make serve-api
 ```
 
-Leave the server running in its terminal.
+From a second terminal, verify:
+```
+make test-2
+```
 
 ---
 
@@ -63,49 +88,53 @@ Find where the issue originates and fix it so that the scores returned represent
 
 Verify:
 ```
-make test  # TestModel::test_probability_scores must pass
+make test-3
 ```
 
+This test exercises the model in memory. For the **served** model to return probabilities too, re-run `make train` and restart `make serve-model`.
+
 ---
 
 **4. Fix the interests count**
 
-With both servers running, run `make test`. This test fails:
+With both servers running, run `make test-4`. It fails with:
 ```
-TestInterestsAPI::test_basic_response — AssertionError: Incorrect number of interests
+AssertionError: Incorrect number of interests
 ```
 
-Fix the API so it returns the correct number of interests. Verify:
+The test asks for 15 interests but never tells the API how many it wants. Make the request send `top_k`, and make sure the API honours it. Verify:
 ```
-make test  # test_basic_response must pass (interests count assertion)
+make test-4
 ```
 
+This is the one task where you edit a test.
+
 ---
 
 **5. Fix response time**
 
-With both servers running, run `make test`. This test fails:
+With both servers running, run `make test-5`. It fails with:
 ```
-TestInterestsAPI::test_basic_response — AssertionError: Request greater than 1 second
+AssertionError: Request greater than 1 second
 ```
 
 Find the performance bottleneck and fix it. Verify:
 ```
-make test  # test_basic_response must pass (timing assertion)
+make test-5
 ```
 
 ---
 
 **6. Add probability to the response**
 
-With both servers running, run `make test`. This test fails:
+With both servers running, run `make test-6`. It fails with:
 ```
-TestInterestsAPI::test_with_probability_threshold
+AssertionError: Interest object missing 'probability': ...
 ```
 
 Update the API response so each interest includes a `probability` field. Verify:
 ```
-make test  # test_with_probability_threshold must pass
+make test-6
 ```
 
 ---
@@ -118,4 +147,7 @@ Implement a feature that lets API clients filter results by a minimum probabilit
 GET /interests/<user_handle>?min_probability=0.5
 ```
 
-Should return only interests with probability ≥ 0.5. There is no automated test for this task — demonstrate it works with a curl request.
+Should return only interests with probability ≥ 0.5. There is no automated test for this task — check the response yourself:
+```
+make test-7
+```
diff --git a/Makefile b/Makefile
index 9468596..76b8e42 100644
--- a/Makefile
+++ b/Makefile
@@ -1,9 +1,32 @@
+PYTEST = TF_CPP_MIN_LOG_LEVEL=3 pytest
+HANDLE ?= e337a675-46f5-437e-aa72-5d43643b5461
+
+.PHONY: help setup serve-api serve-model ping-model train test \
+	test-1 test-2 test-3 test-4 test-5 test-6 test-7
+
+help:
+	@printf 'Setup and servers\n'
+	@printf '  make setup        Install dependencies\n'
+	@printf '  make train        Train the model and export it to serving/\n'
+	@printf '  make serve-model  Start TF Serving on port 8501\n'
+	@printf '  make serve-api    Start the Flask API on port 5005\n'
+	@printf '  make ping-model   Check that TF Serving has loaded the model\n'
+	@printf '\nInterview tasks (run only the target for the task you are on)\n'
+	@printf '  make test-1       Task 1: model build\n'
+	@printf '  make test-2       Task 2: API starts up\n'
+	@printf '  make test-3       Task 3: probability scores\n'
+	@printf '  make test-4       Task 4: interests count\n'
+	@printf '  make test-5       Task 5: response time\n'
+	@printf '  make test-6       Task 6: probability in the response\n'
+	@printf '  make test-7       Task 7: min_probability filtering\n'
+	@printf '  make test         Every test at once (expect noise until all tasks are done)\n'
+
 setup:
 	pip install -r requirements.txt
 
 serve-api:
 	python -m flask --app api/app run --debug --port 5005 --host 0.0.0.0
-	
+
 serve-model:
 	docker compose up tf-serving
 
@@ -14,4 +37,30 @@ train:
 	TF_CPP_MIN_LOG_LEVEL=3 python -m model.main
 
 test:
-	TF_CPP_MIN_LOG_LEVEL=3 pytest ./tests -p no:warnings
\ No newline at end of file
+	$(PYTEST)
+
+test-1:
+	$(PYTEST) tests/test_model.py::TestModel::test_model_build
+
+# No automated test — the API only starts once the bug is fixed.
+test-2:
+	@curl -fs http://localhost:5005/ \
+		&& printf '\nPASS: the API is up\n' \
+		|| printf 'FAIL: the API is not reachable on port 5005 (see task 2)\n'
+
+test-3:
+	$(PYTEST) tests/test_model.py::TestModel::test_probability_scores
+
+test-4:
+	$(PYTEST) tests/test_app.py::TestInterestsAPI::test_interests_count
+
+test-5:
+	$(PYTEST) tests/test_app.py::TestInterestsAPI::test_response_time
+
+test-6:
+	$(PYTEST) tests/test_app.py::TestInterestsAPI::test_with_probability_threshold
+
+# No automated test — read the response and check every probability is >= 0.5.
+test-7:
+	@curl -fsS "http://localhost:5005/interests/$(HANDLE)?min_probability=0.5" \
+		| python3 -m json.tool
diff --git a/README.md b/README.md
index c709418..236dbb0 100644
--- a/README.md
+++ b/README.md
@@ -23,11 +23,25 @@ Once the container starts, dependencies are installed automatically via `make se
 
 ### Test
 
+Each interview task has its own target, so you only see the output for the task you are working on:
+
+| Command | Task |
+|---|---|
+| `make test-1` | 1 — model build |
+| `make test-2` | 2 — API starts up |
+| `make test-3` | 3 — probability scores |
+| `make test-4` | 4 — interests count |
+| `make test-5` | 5 — response time |
+| `make test-6` | 6 — probability in the response |
+| `make test-7` | 7 — `min_probability` filtering |
+
 ```
 make test
 ```
 
-Runs all tests in `./tests` with pytest. Use this to verify each task as you work through the interview.
+Runs every test in `./tests` at once. Prefer the per-task targets while working — tests for tasks you have not reached yet will fail and make the output hard to read.
+
+Run `make` on its own to list every available command.
 
 ### Train
 
diff --git a/pytest.ini b/pytest.ini
new file mode 100644
index 0000000..5db2bee
--- /dev/null
+++ b/pytest.ini
@@ -0,0 +1,3 @@
+[pytest]
+testpaths = tests
+addopts = -q --no-header --tb=short -p no:warnings -p no:cacheprovider
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..a8b2d31
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,31 @@
+import pytest
+import requests
+
+API_URL = "http://localhost:5005/"
+MODEL_URL = "http://localhost:8501/v1/models/interests-model"
+
+
+def _is_up(url):
+    try:
+        requests.get(url, timeout=2).raise_for_status()
+    except requests.RequestException:
+        return False
+    return True
+
+
+@pytest.fixture(scope="session")
+def _servers_running():
+    """Fail with a readable message instead of a ConnectionError traceback."""
+    if not _is_up(MODEL_URL):
+        pytest.fail(
+            "TF Serving is not reachable on port 8501 — "
+            "run `make train`, then `make serve-model`.",
+            pytrace=False,
+        )
+
+    if not _is_up(API_URL):
+        pytest.fail(
+            "The Flask API is not reachable on port 5005 — "
+            "run `make serve-api` (see task 2).",
+            pytrace=False,
+        )
diff --git a/tests/test_app.py b/tests/test_app.py
index 86bf5f6..673e36c 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -1,24 +1,24 @@
 import time
 
+import pytest
 import requests
 
+HTTP_OK = 200
 
+
+@pytest.mark.usefixtures("_servers_running")
 class TestInterestsAPI:
     BASE_URL = "http://localhost:5005/interests"
 
-    def make_request(self, user_handle):
-        return requests.get(f"{self.BASE_URL}/{user_handle}")
+    def make_request(self, user_handle, **params):
+        return requests.get(f"{self.BASE_URL}/{user_handle}", params=params)
 
     def test_basic_response(self):
         user_handle = "e337a675-46f5-437e-aa72-5d43643b5461"
-        top_k = 15
 
-        start_time = time.time()
         response = self.make_request(user_handle=user_handle)
-        end_time = time.time()
-        request_time = end_time - start_time
 
-        assert response.status_code == 200, "Status code is not 200"
+        assert response.status_code == HTTP_OK, "Status code is not 200"
 
         response = response.json()
 
@@ -26,9 +26,29 @@ def test_basic_response(self):
 
         assert isinstance(response["interests"], list), "Interests is not a list"
 
+    def test_interests_count(self):
+        user_handle = "e337a675-46f5-437e-aa72-5d43643b5461"
+        top_k = 15
+
+        response = self.make_request(user_handle=user_handle)
+
+        assert response.status_code == HTTP_OK, "Status code is not 200"
+
+        response = response.json()
+
         assert len(response["interests"]) == top_k, "Incorrect number of interests"
 
-        assert request_time < 1, "Request greater than 1 seconds"
+    def test_response_time(self):
+        user_handle = "e337a675-46f5-437e-aa72-5d43643b5461"
+
+        start_time = time.time()
+        response = self.make_request(user_handle=user_handle)
+        end_time = time.time()
+        request_time = end_time - start_time
+
+        assert response.status_code == HTTP_OK, "Status code is not 200"
+
+        assert request_time < 1, "Request greater than 1 second"
 
     def test_with_probability_threshold(self):
         user_handle = "e337a675-46f5-437e-aa72-5d43643b5461"