Missing handling of pkg:cpan causes tests to fail

[petergardfjall]

Unit tests are currently failing on master because the implementation does not properly validate pkg:cpan as prescribed by the spec.

That, I reckon, is a major downside of keeping tests in a separate repository.

$ make test 
curl -Ls https://raw.githubusercontent.com/package-url/purl-spec/master/test-suite-data.json -o testdata/test-suite-data.json
go test -v -cover ./...
=== RUN   TestFromStringExamples
    packageurl_test.go:183: cpan module name like distribution name did not fail and returned packageurl.PackageURL{Type:"cpan", Namespace:"", Name:"Perl-Version", Version:"1.013", Qualifiers:packageurl.Qualifiers{}, Subpath:""}
    packageurl_test.go:183: cpan distribution name like module name did not fail and returned packageurl.PackageURL{Type:"cpan", Namespace:"GDT", Name:"URI::PackageURL", Version:"2.11", Qualifiers:packageurl.Qualifiers{}, Subpath:""}
--- FAIL: TestFromStringExamples (0.00s)
=== RUN   TestToStringExamples
--- PASS: TestToStringExamples (0.00s)
=== RUN   TestStringer
--- PASS: TestStringer (0.00s)
=== RUN   TestQualifiersMapConversion
--- PASS: TestQualifiersMapConversion (0.00s)
=== RUN   TestNameEscaping
=== RUN   TestNameEscaping/abc
=== RUN   TestNameEscaping/ab/c
--- PASS: TestNameEscaping (0.00s)
    --- PASS: TestNameEscaping/abc (0.00s)
    --- PASS: TestNameEscaping/ab/c (0.00s)
=== RUN   TestQualifierMissingEqual
--- PASS: TestQualifierMissingEqual (0.00s)
=== RUN   TestNormalize
=== RUN   TestNormalize/type_is_case_insensitive
=== RUN   TestNormalize/type_is_manditory
=== RUN   TestNormalize/leading_and_traling_/_on_namespace_are_trimmed
=== RUN   TestNormalize/qualifiers_with_empty_values_are_removed
=== RUN   TestNormalize/qualifiers_are_sorted_by_key
=== RUN   TestNormalize/duplicate_keys_are_invalid
=== RUN   TestNormalize/keys_are_made_lower_case
=== RUN   TestNormalize/name_is_required
=== RUN   TestNormalize/leading_and_traling_/_on_subpath_are_trimmed
=== RUN   TestNormalize/'.'_is_an_invalid_subpath_segment
=== RUN   TestNormalize/'..'_is_an_invalid_subpath_segment
=== RUN   TestNormalize/'./'_is_a_valid_subpath_prefix
=== RUN   TestNormalize/'../'_is_a_valid_subpath_prefix
=== RUN   TestNormalize/known_type_namespace_adjustments
=== RUN   TestNormalize/known_type_name_adjustments
=== RUN   TestNormalize/known_type_version_adjustments
--- PASS: TestNormalize (0.00s)
    --- PASS: TestNormalize/type_is_case_insensitive (0.00s)
    --- PASS: TestNormalize/type_is_manditory (0.00s)
    --- PASS: TestNormalize/leading_and_traling_/_on_namespace_are_trimmed (0.00s)
    --- PASS: TestNormalize/qualifiers_with_empty_values_are_removed (0.00s)
    --- PASS: TestNormalize/qualifiers_are_sorted_by_key (0.00s)
    --- PASS: TestNormalize/duplicate_keys_are_invalid (0.00s)
    --- PASS: TestNormalize/keys_are_made_lower_case (0.00s)
    --- PASS: TestNormalize/name_is_required (0.00s)
    --- PASS: TestNormalize/leading_and_traling_/_on_subpath_are_trimmed (0.00s)
    --- PASS: TestNormalize/'.'_is_an_invalid_subpath_segment (0.00s)
    --- PASS: TestNormalize/'..'_is_an_invalid_subpath_segment (0.00s)
    --- PASS: TestNormalize/'./'_is_a_valid_subpath_prefix (0.00s)
    --- PASS: TestNormalize/'../'_is_a_valid_subpath_prefix (0.00s)
    --- PASS: TestNormalize/known_type_namespace_adjustments (0.00s)
    --- PASS: TestNormalize/known_type_name_adjustments (0.00s)
    --- PASS: TestNormalize/known_type_version_adjustments (0.00s)
=== RUN   FuzzFromString
=== RUN   FuzzFromString/771e938e4458e983a736261a702e27c7a414fd660a15b63034f290b146d2f217
0=== RUN   FuzzFromString/d0a861fe9b7c443af2b649e08753442111b630dd29fcd570543db3f9351158aa
?A--- PASS: FuzzFromString (0.00s)
    --- PASS: FuzzFromString/771e938e4458e983a736261a702e27c7a414fd660a15b63034f290b146d2f217 (0.00s)
    --- PASS: FuzzFromString/d0a861fe9b7c443af2b649e08753442111b630dd29fcd570543db3f9351158aa (0.00s)
FAIL
coverage: 89.0% of statements
FAIL	github.com/package-url/packageurl-go	0.004s
FAIL
make: *** [Makefile:5: test] Error 1

[petergardfjall]

I opened #79 to address this issue.