When would you use Testcontainers, SQLite, or EF Core InMemory for data-access tests?

Choose Testcontainers, SQLite, or EF Core InMemory

Chooses database test infrastructure by the provider behavior a test must prove.

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TL;DR

EF Core InMemory is useful for simple application logic that needs a lightweight store, but it is not relational and does not prove SQL translation, constraints, or transactions. SQLite is relational and fast, but its types, SQL dialect, and concurrency differ from SQL Server or PostgreSQL. Testcontainers runs the real database engine, so it is the strongest choice when provider behavior matters.

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Provider fidelity, SQL translation, constraints, transactions, speed, setup cost, and layered suites.

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Why this question matters
All three options can execute tests, but they do not provide the same evidence. Provider differences matter precisely where data-access defects tend to hide.
EF Core InMemory is useful for simple application logic that needs a lightweight store, but it is not relational and does not prove SQL translation, constraints, or transactions. SQLite is relational and fast, but its types, SQL dialect, and concurrency differ from SQL Server or PostgreSQL. Testcontainers runs the real database engine, so it is the strongest choice when provider behavior matters.
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Stronger answer
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I use the lightest option that preserves the behavior under test. A repository-free domain rule needs no database. Basic persistence wiring might use SQLite if production-specific behavior is irrelevant. Queries, migrations, collations, indexes, rowversion, locking, and provider-specific SQL should run against the production engine, usually through a disposable container. Speed is managed through shared infrastructure and isolated data, not by replacing away the risk.

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Details

Treating EF Core InMemory as a SQL Server emulator.
Using SQLite for provider-specific migrations.
Starting a new container for every tiny assertion.
Assuming containers reproduce managed production services completely.

When would you use Testcontainers, SQLite, or EF Core InMemory for data-access tests?

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When would you use Testcontainers, SQLite, or EF Core InMemory for data-access tests?

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