test(tvix/eval): add identity tests for literal evaluation

Change-Id: Id3f37fbe341e15e9428ef1d579d61a514232c0e8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6132
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>

tvix/eval/src/tests/tvix_tests/README.md

@@ -0,0 +1,19 @@
+These tests are "native" to Tvix and exist in addition to the Nix test
+suite.
+
+All of these are straightforward code snippets which are expected to
+produce a certain result.
+
+# `identity-*` tests
+
+Files named `identity-*.nix` contain code that is supposed to produce
+itself exactly after evaluation.
+
+These are useful for testing literals.
+
+# `eval-okay-*` tests
+
+Files named `eval-okay-*.nix` contain code which is supposed to
+evaluate to the output in the corresponding `eval-okay-*.exp` file.
+
+This convention is taken from the original Nix test suite.

tvix/eval/src/tests/tvix_tests/identity-bool-false.nix

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+false

tvix/eval/src/tests/tvix_tests/identity-bool-true.nix

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+true

tvix/eval/src/tests/tvix_tests/identity-empty-attrs.nix

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+{ }

tvix/eval/src/tests/tvix_tests/identity-empty-list.nix

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+[ ]

tvix/eval/src/tests/tvix_tests/identity-flat-attrs.nix

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+{ a = 15; b = "string"; c = null; }

tvix/eval/src/tests/tvix_tests/identity-float.nix

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+4.2

tvix/eval/src/tests/tvix_tests/identity-heterogeneous-list.nix

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+[ 1 2.1 "three" null ]

tvix/eval/src/tests/tvix_tests/identity-homogeneous-float-list.nix

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+[ 4.2 6.9 13.37 ]

tvix/eval/src/tests/tvix_tests/identity-homogeneous-int-list.nix

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+[ 0 1 2 3 4 5 7 8 9 ]

tvix/eval/src/tests/tvix_tests/identity-homogeneous-string-list.nix

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+[ "string" "list" ]

tvix/eval/src/tests/tvix_tests/identity-int.nix

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+42

tvix/eval/src/tests/tvix_tests/identity-kv-attrs.nix

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+{ name = "foo"; value = 12; }

tvix/eval/src/tests/tvix_tests/identity-nested-attrs.nix

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+{ a = { b = null; }; }

tvix/eval/src/tests/tvix_tests/identity-null.nix

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+null

tvix/eval/src/tests/tvix_tests/identity-signed-float.nix

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+-4.2

tvix/eval/src/tests/tvix_tests/identity-signed-int.nix

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+-42

tvix/eval/src/tests/tvix_tests/identity-string.nix

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+"test string"