feat: migrate assertions from gotest.tools to testify

[Harsh-Daga]

This PR migrates all test assertions from gotest.tools/v3/assert to github.com/stretchr/testify/assert, consolidating the codebase on a single testing library. The migration maintains full test coverage and behavior.

Implementation Details

Assertion Mapping:

• assert.NilError(t, err) → assert.NoError(t, err)
• assert.Assert(t, condition) → assert.True(t, condition)
• assert.Check(t, condition) → assert.True(t, condition)
• cmp.Equal(a, b) → assert.Equal(t, expected, actual)
• cmp.Len(obj, n) → assert.Len(t, obj, n)
• cmp.Contains(str, substr) → assert.Contains(t, str, substr)
• cmp.DeepEqual(a, b) → assert.Equal(t, expected, actual) for simple cases

Complex Comparisons:
For tests requiring cmpopts (specifically helpers_test.go), I retained google/go-cmp directly and used assert.Empty(t, cmp.Diff(expected, actual, opts)) pattern. This preserves the powerful comparison options needed for complex struct comparisons while still using testify for the assertion.

Files Migrated (24 total):

Command packages:

• cmd/gen-source-variants/main_test.go
• cmd/test2json2gha/event_test.go
• cmd/test2json2gha/github_test.go
• cmd/test2json2gha/main_test.go
• cmd/test2json2gha/summary_test.go

Root level:

• helpers_test.go
• load_test.go
• source_test.go
• spec_test.go

Package tests:

• linters/yaml_json_tags_test.go
• packaging/linux/deb/template_rules_test.go
• packaging/linux/rpm/template_test.go
• sessionutil/socketprovider/proxy_test.go

Test directory:

• test/cache_test.go
• test/handlers_test.go
• test/helpers_test.go
• test/linux_target_test.go
• test/network_test.go
• test/signing_test.go
• test/source_test.go
• test/windows_test.go

Test utilities:

• test/testenv/buildx.go

Testing

All existing tests continue to pass with the new assertions:

go test -short ./...

Build verification:
go build ./...

I verified that:

1. All test files compile without errors
2. All existing test cases pass with identical behavior
3. No test logic was changed, only assertion syntax
4. Dependencies were properly cleaned up with go mod tidy

Notes

• gotest.tools/v3/skip is intentionally retained in some test files as testify does not provide equivalent skip functionality
• The gotest.tools/v3 dependency remains in go.mod solely for the skip package usage
• Test behavior is unchanged; this is purely a syntactic migration
• Argument order in assert.Equal follows testify convention: assert.Equal(t, expected, actual)

Fixes #913

[invidian]

@Harsh-Daga Assert from gotest.tools/v3/assert will FailNow() the tests, so we should actually use github.com/stretchr/testify/require to preserve that behaviour.