How deeply does 100 Go Mistakes and How to Avoid Them cover mutable shared state?

Explains how a global clock couples tests, then contrasts struct-level clock injection with caller-supplied timestamps.

Mutable shared state

As explained in 100 Go Mistakes and How to Avoid Them

Mutable shared state is data that can be modified and is accessible by multiple parts of a program or concurrent executions.

A package-level clock such as `var now = time.Now` is mutable shared state. Tests that depend on it are coupled through the same variable and cannot safely run in parallel. section 11.6

For time-dependent cache tests, inject a `func() time.Time` into the cache and provide a fixed-time implementation. If external-package tests cannot access that dependency, let callers supply the time or cutoff; passing a cutoff is simplest and needs no stub type. section 11.6

var now = time.Now      #1

This package-level clock illustrates the shared-variable approach that can couple tests. section 11.6

How 100 Go Mistakes and How to Avoid Them covers it

Cover of 100 Go Mistakes and How to Avoid Them

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Also explained in

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C++ Concurrency in Action, Second EditionShared mutable data is information accessible by multiple threads that can also be modified during execution.

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Related concepts

integration testused by · An integration test evaluates whether multiple software components, or a component and an external dependency, interact and behave correctly together.
threadused by · A thread is an independently schedulable sequence or context of execution within a program or process.
actorused by · An actor is an independent entity or participant that performs actions, maintains or pursues state or goals, and interacts with other entities or systems.
synchronizationconfigured by · Synchronization coordinates operations, events, clocks, data, or states to establish required timing, ordering, visibility, or consistency relationships.
flaky testproduces · A flaky test is an automated test whose outcome varies across executions under equivalent conditions without a relevant change to the software or test intent.

This explainer was generated by Manning's knowledge graph from the text of 100 Go Mistakes and How to Avoid Them. The section links point to the parts of the book it draws on.