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Purpose

Unit Test Coverage shows a percentage of a source code covered by unit tests. It is a mix of Line coverage and Condition coverage. The metric can be also calculated for a new code only.

How metric helps

Unit Test Coverage may be a guide for indicating a lack of coverage via Automated Testing - just because Unit Testing is the essential part of the Testing Pyramid. A trend helps to understand how a coverage is changing over time, if it is actually growing or falling and how those trends correlate with plans/investments about appropriate development efforts related to Unit Tests. Lack of coverage is typically a key obstacle for implementing the Continuous Integration and Continuous Delivery  (CI/CD) on a project.

Metric:

• shows a percentage

  of 

  of a source code covered by unit tests;

• shows quality of application;

• shows quality of testing;

• shows how the project is ready for implementation of CI/CD;

• shows if the projects meets the industry quality standards;

• highlights the risk of bugs being detected at a later stage of development;

• helps to understand how much of your source is tested;

• shows the quality of test suite.

TOP-5 problems metric identifies 

1. No

   Lack of focus on

   quality of software

   Quality

2. Technical and Quality Debt

   / Tech Debt / EngX processes are not included into deliveryThere is no Test Plan and/

   is out of control

3. No Test Plan or Strategy

4. Too many defects are found during manual and / or automated testing

5. Team misbalance (skills ratio)

How metric works

Chart overview

Chart shows Unit Tests Coverage in %:
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Calculation

Unit Test Coverage = (CT + CF + LC) / (2*B + EL),

where

• CT = conditions that have been evaluated to 'true' at least once 

• CF = conditions that have been evaluated to 'false' at least once

• LC = covered lines = lines_to_cover - uncovered_lines

• B = total number of conditions

• EL = total number of executable lines (lines_to_cover)

RAG thresholds: Red <= 40%, Amber > 40%, Green > 80 %.Unit Test Coverage for a New Code, % calculation is Identical to Unit Test Coverage but restricted to new/updated source code.

Data source

Data for the metric can be collected from Sonar.