lab-01-explore-demo-apps

permalink	/labs/lab-01-explore-demo-apps/
title	Lab 01: Explore Demo Apps
description	Browse the 5 demo applications, understand their intentional violations, and run each app locally with Docker.

Lab 01: Explore Demo Apps

Duration	Level	Prerequisites
30 min	Beginner	Lab 00

Learning Objectives

• Understand the 5-app, 5-language demo application structure
• Identify the types of intentional code quality violations embedded in each app
• Run each demo app locally with Docker
• Navigate the repository layout and understand how files relate to scanning tools

Prerequisites

• Completed Lab 00: Prerequisites
• The code-quality-scan-demo-app repository cloned locally

Exercises

Exercise 1: Explore the Repository Structure

Working Directory: Run the following commands from the code-quality-scan-demo-app repository root.

View the top-level directory structure:

Get-ChildItem -Directory | Format-Table Name, LastWriteTime

You should see the following key directories:

Directory	Language	Framework
cq-demo-app-001	TypeScript	Express
cq-demo-app-002	Python	Flask
cq-demo-app-003	C#	ASP.NET Core
cq-demo-app-004	Java	Spring Boot
cq-demo-app-005	Go	net/http

Additional directories include src/converters/ (SARIF converters), src/config/ (tool configurations), scripts/ (bootstrap and data pipeline), and power-bi/ (PBIP dashboard).

Exercise 2: Explore cq-demo-app-001 (TypeScript / Express)

Browse the TypeScript demo app:

Get-ChildItem cq-demo-app-001 -Recurse -File | Select-Object FullName | Select-Object -First 20

Key files to examine:

File	Purpose
src/index.ts	Express server entry point
src/routes/	API route handlers
src/utils/	Utility functions with complexity/duplication violations
Dockerfile	Multi-stage Docker build
infra/main.bicep	Azure deployment infrastructure
eslint.config.mjs	ESLint configuration

Intentional violations in this app:

• prefer-const violations (using let where const should be used)
• Unused variables and imports
• Functions with cyclomatic complexity > 10
• Duplicated utility functions
• Low test coverage (< 50%)

Build and run the app:

cd cq-demo-app-001
docker build -t cq-demo-app-001 .
docker run -d -p 3000:3000 --name app001 cq-demo-app-001

Open http://localhost:3000 to see the running app.

Clean up:

docker stop app001; docker rm app001
cd ..

Exercise 3: Explore cq-demo-app-002 (Python / Flask)

Browse the Python demo app:

Get-ChildItem cq-demo-app-002 -Recurse -File | Select-Object FullName | Select-Object -First 20

Key files:

File	Purpose
src/app.py	Flask application entry point
src/services/	Business logic with violations
src/utils/	Utility functions
pyproject.toml	Python project config with Ruff settings
Dockerfile	Container build definition

Intentional violations:

• Unused imports and variables (Ruff F401, F841)
• Missing type annotations
• Functions exceeding 50 lines
• Duplicated data validation logic
• Minimal test coverage

Build and run:

cd cq-demo-app-002
docker build -t cq-demo-app-002 .
docker run -d -p 5000:5000 --name app002 cq-demo-app-002

Open http://localhost:5000 to verify.

Clean up:

docker stop app002; docker rm app002
cd ..

Exercise 4: Explore cq-demo-app-003 (C# / ASP.NET Core)

Browse the C# demo app:

Get-ChildItem cq-demo-app-003 -Recurse -File -Include *.cs,*.csproj,*.bicep,Dockerfile | Select-Object FullName | Select-Object -First 20

Key files:

File	Purpose
src/Program.cs	ASP.NET Core entry point
src/Controllers/	API controllers
src/Services/	Business logic with violations
src/*.csproj	Project file with analyzer settings
.editorconfig	.NET Analyzer rules

Intentional violations:

• CA1822 (methods that can be made static)
• CA2007 (missing ConfigureAwait)
• High cyclomatic complexity in data processing methods
• Duplicated validation logic across controllers
• Missing unit tests for service layer

Build and run:

cd cq-demo-app-003
docker build -t cq-demo-app-003 .
docker run -d -p 8080:8080 --name app003 cq-demo-app-003

Open http://localhost:8080 to verify.

Clean up:

docker stop app003; docker rm app003
cd ..

Exercise 5: Explore cq-demo-app-004 (Java / Spring Boot)

Browse the Java demo app:

Get-ChildItem cq-demo-app-004 -Recurse -File -Include *.java,pom.xml,Dockerfile | Select-Object FullName | Select-Object -First 20

Key files:

File	Purpose
src/main/java/.../Application.java	Spring Boot entry point
src/main/java/.../controllers/	REST controllers
src/main/java/.../services/	Service layer with violations
pom.xml	Maven build with Checkstyle plugin
checkstyle.xml	Checkstyle configuration

Intentional violations:

• Checkstyle naming convention violations
• Methods exceeding recommended length
• Deeply nested conditionals (> 4 levels)
• Copy-pasted utility methods
• Missing JUnit test cases

Build and run:

cd cq-demo-app-004
docker build -t cq-demo-app-004 .
docker run -d -p 8080:8080 --name app004 cq-demo-app-004

Open http://localhost:8080 to verify.

Clean up:

docker stop app004; docker rm app004
cd ..

Exercise 6: Explore cq-demo-app-005 (Go / net/http)

Browse the Go demo app:

Get-ChildItem cq-demo-app-005 -Recurse -File -Include *.go,go.mod,Dockerfile | Select-Object FullName | Select-Object -First 20

Key files:

File	Purpose
main.go	HTTP server entry point
handlers/	Request handler functions
utils/	Utility functions with violations
go.mod	Go module definition
.golangci.yml	golangci-lint configuration

Intentional violations:

• errcheck — unchecked error returns
• ineffassign — ineffective assignments
• High cyclomatic complexity in parsing functions
• Duplicated string processing logic
• No test files (*_test.go)

Build and run:

cd cq-demo-app-005
docker build -t cq-demo-app-005 .
docker run -d -p 8080:8080 --name app005 cq-demo-app-005

Open http://localhost:8080 to verify.

Clean up:

docker stop app005; docker rm app005
cd ..

Exercise 7: Preview Code Quality Issues

Open any demo app in VS Code and look for common violation patterns:

code cq-demo-app-001

Look for these patterns:

1. Unused variables: Variables declared but never referenced
2. Long functions: Functions with more than 50 lines
3. Nested conditions: if/else chains nested 4+ levels deep
4. Copy-pasted blocks: Similar code blocks in different files
5. Missing tests: Source files without corresponding test files

Verification Checkpoint

Verify your work before continuing:

• You can list all 5 demo app directories (cq-demo-app-001 through 005)
• You successfully built and ran at least one demo app with Docker
• You can identify at least 3 types of intentional violations in the source code
• You understand the purpose of src/converters/, src/config/, and scripts/ directories

Summary

The code-quality-scan-demo-app repository contains 5 demo applications, each written in a different language and framework. Every app includes intentional code quality violations — lint errors, high complexity, code duplication, and low test coverage — that you will detect and remediate in subsequent labs.

All apps follow a consistent structure with source code, Dockerfile, Bicep infrastructure, and a deploy workflow. They can all be built and run locally with Docker, making them ideal for hands-on scanning exercises.

Next Steps

Proceed to Lab 02: Linting.