The purpose of a database is to keep your data safe and organized. The SQLite development team is aware that nobody will use a database product that has a reputation for being buggy or unreliable. To maintain a high level of reliability, the core SQLite library is aggressively tested before each release.
In full, the standard SQLite test suites consists of over 10 million unit tests and query tests. The “soak test,” done prior to each release, consists of over 2.5 billion tests. The suite provides 100% statement coverage and 100% branch coverage, including edge-case errors, such as out-of-memory and out-of-storage conditions. The test suite is designed to push the system to its specified limits and beyond, providing extensive coverage of both code and operating parameters.
This high level of testing keeps the SQLite bug count relatively low. No software is perfect, but bugs that contribute to actual data-loss or database corruption are fairly rare. Most bugs that escape are performance related, where the database will do the right thing, but in the wrong way, leading to longer run-times.
Strong testing also keeps backwards compatibility extremely solid. The SQLite team takes backwards compatibility very seriously. File formats, SQL syntax, and programming APIs and behaviors have an extremely strong history of backwards compatibility. Updating to a new version of SQLite rarely causes compatibility problems.
In addition to keeping the core library reliable, the extensive testing also frees the SQLite developers to be more experimental. Whole subsystems of the SQLite code can be (and have been) ripped out and updated or replaced, with little concern about compatibility or functional differences—as long as all the tests pass. This allows the team to make significant changes with relatively little risk, constantly pushing the product and performance forward.
Like so many other aspects of the SQLite design, fewer bugs means fewer problems and less to worry about. As much as any complex piece of software can, it just works.
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