83 lines
2.6 KiB
Markdown
83 lines
2.6 KiB
Markdown
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# Testers {#chap-testers}
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This chapter describes several testing builders which are available in the <literal>testers</literal> namespace.
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## `testVersion` {#tester-testVersion}
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Checks the command output contains the specified version
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Although simplistic, this test assures that the main program
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can run. While there's no substitute for a real test case,
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it does catch dynamic linking errors and such. It also provides
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some protection against accidentally building the wrong version,
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for example when using an 'old' hash in a fixed-output derivation.
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Examples:
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```nix
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passthru.tests.version = testVersion { package = hello; };
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passthru.tests.version = testVersion {
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package = seaweedfs;
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command = "weed version";
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};
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passthru.tests.version = testVersion {
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package = key;
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command = "KeY --help";
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# Wrong '2.5' version in the code. Drop on next version.
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version = "2.5";
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};
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```
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## `testEqualDerivation` {#tester-testEqualDerivation}
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Checks that two packages produce the exact same build instructions.
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This can be used to make sure that a certain difference of configuration,
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such as the presence of an overlay does not cause a cache miss.
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When the derivations are equal, the return value is an empty file.
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Otherwise, the build log explains the difference via `nix-diff`.
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Example:
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```nix
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testEqualDerivation
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"The hello package must stay the same when enabling checks."
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hello
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(hello.overrideAttrs(o: { doCheck = true; }))
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```
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## `invalidateFetcherByDrvHash` {#tester-invalidateFetcherByDrvHash}
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Use the derivation hash to invalidate the output via name, for testing.
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Type: `(a@{ name, ... } -> Derivation) -> a -> Derivation`
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Normally, fixed output derivations can and should be cached by their output
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hash only, but for testing we want to re-fetch everytime the fetcher changes.
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Changes to the fetcher become apparent in the drvPath, which is a hash of
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how to fetch, rather than a fixed store path.
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By inserting this hash into the name, we can make sure to re-run the fetcher
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every time the fetcher changes.
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This relies on the assumption that Nix isn't clever enough to reuse its
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database of local store contents to optimize fetching.
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You might notice that the "salted" name derives from the normal invocation,
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not the final derivation. `invalidateFetcherByDrvHash` has to invoke the fetcher
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function twice: once to get a derivation hash, and again to produce the final
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fixed output derivation.
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Example:
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```nix
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tests.fetchgit = invalidateFetcherByDrvHash fetchgit {
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name = "nix-source";
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url = "https://github.com/NixOS/nix";
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rev = "9d9dbe6ed05854e03811c361a3380e09183f4f4a";
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sha256 = "sha256-7DszvbCNTjpzGRmpIVAWXk20P0/XTrWZ79KSOGLrUWY=";
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};
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```
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