My original intention was just to reduce our number of dependencies by
standardizing on a single comparison library, but in the process of doing
so I found various examples of the kinds of problems that caused this
codebase to begin adopting go-cmp instead of go-test/deep in the first
place, which make it easy to accidentally write a false-positive test that
doesn't actually check what the author thinks is being checked:
- deep.Equal silently ignores unexported fields, so comparing two values
that differ only in data in unexported fields succeeds even when it ought
not to.
TestContext2Apply_multiVarComprehensive in package tofu was an excellent
example of this problem: it had various test assertions that were
actually checking absolutely nothing, despite appearing to compare
pairs of cty.Value.
- deep.Equal also silently ignores anything below a certain level of
nesting, and so comparison of deep data structures can appear to succeed
even though they don't actually match.
There were a few examples where that problem had already been found and
fixed by temporarily overriding the package deep global settings, but
with go-cmp the default behavior already visits everything, or panics
if it cannot.
This does mean that in a few cases this needed some more elaborate options
to cmp.Diff to align with the previous behavior, which is a little annoying
but overall I think better to be explicit about what each test is relying
on. Perhaps we can rework these tests to need fewer unusual cmp options
in future, but for this commit I want to keep focused on the smallest
possible changes to remove our dependency on github.com/go-test/deep .
Signed-off-by: Martin Atkins <mart@degeneration.co.uk>
