Improve testing & expand sectional examples

Doing this in one big gulp because I wanted to reuse tests in order to
insure that sectional and non-sectional codeowners files are processed
similarly

ee/spec/fixtures/mixed_case_sectional_codeowners_example

-ee/ @gl-admin
+# This is an example code owners file, lines starting with a `#` will
+# be ignored.
+
+# app/ @commented-rule
+
+# We can specify a default match using wildcards:
+* @default-codeowner
+
+# Rules defined later in the file take precedence over the rules
+# defined before.
+# This will match all files for which the file name ends in `.rb`
+*.rb @ruby-owner
+
+# Files with a `#` can still be accesssed by escaping the pound sign
+\#file_with_pound.rb @owner-file-with-pound
+
+# Multiple codeowners can be specified, separated by whitespace
+CODEOWNERS @multiple @owners	@tab-separated
+
+# Both usernames or email addresses can be used to match
+# users. Everything else will be ignored. For example this will
+# specify `@legal` and a user with email `janedoe@gitlab.com` as the
+# owner for the LICENSE file
+LICENSE @legal this does not match janedoe@gitlab.com
+
+# Ending a path in a `/` will specify the code owners for every file
+# nested in that directory, on any level
+/docs/ @all-docs
+
+# Ending a path in `/*` will specify code owners for every file in
+# that directory, but not nested deeper. This will match
+# `docs/index.md` but not `docs/projects/index.md`
+/docs/* @root-docs
+
+# This will make a `lib` directory nested anywhere in the repository
+# match
+lib/ @lib-owner
+
+# This will only match a `config` directory in the root of the
+# repository
+/config/ @config-owner
+
+# If the path contains spaces, these need to be escaped like this:
+path\ with\ spaces/ @space-owner
 
 [Documentation]
 ee/docs    @gl-docs

ee/spec/fixtures/sectional_codeowners_example

-ee/ @gl-admin
+# This is an example code owners file, lines starting with a `#` will
+# be ignored.
+
+# app/ @commented-rule
+
+# We can specify a default match using wildcards:
+* @default-codeowner
+
+# Rules defined later in the file take precedence over the rules
+# defined before.
+# This will match all files for which the file name ends in `.rb`
+*.rb @ruby-owner
+
+# Files with a `#` can still be accesssed by escaping the pound sign
+\#file_with_pound.rb @owner-file-with-pound
+
+# Multiple codeowners can be specified, separated by whitespace
+CODEOWNERS @multiple @owners	@tab-separated
+
+# Both usernames or email addresses can be used to match
+# users. Everything else will be ignored. For example this will
+# specify `@legal` and a user with email `janedoe@gitlab.com` as the
+# owner for the LICENSE file
+LICENSE @legal this does not match janedoe@gitlab.com
+
+# Ending a path in a `/` will specify the code owners for every file
+# nested in that directory, on any level
+/docs/ @all-docs
+
+# Ending a path in `/*` will specify code owners for every file in
+# that directory, but not nested deeper. This will match
+# `docs/index.md` but not `docs/projects/index.md`
+/docs/* @root-docs
+
+# This will make a `lib` directory nested anywhere in the repository
+# match
+lib/ @lib-owner
+
+# This will only match a `config` directory in the root of the
+# repository
+/config/ @config-owner
+
+# If the path contains spaces, these need to be escaped like this:
+path\ with\ spaces/ @space-owner
 
 [Documentation]
 ee/docs    @gl-docs

ee/spec/lib/gitlab/code_owners/file_spec.rb

@@ -52,8 +52,21 @@ describe Gitlab::CodeOwners::File do
           expect(data.keys).to contain_exactly("codeowners", "Documentation", "Database")
         end
 
+        codeowners_section_paths = [
+          "/**/#file_with_pound.rb", "/**/*", "/**/*.rb", "/**/CODEOWNERS",
+          "/**/LICENSE", "/**/lib/**/*", "/**/path with spaces/**/*",
+          "/config/**/*", "/docs/*", "/docs/**/*"
+        ]
+
+        codeowners_section_owners = [
+          "@all-docs", "@config-owner", "@default-codeowner",
+          "@legal this does not match janedoe@gitlab.com", "@lib-owner",
+          "@multiple @owners\t@tab-separated", "@owner-file-with-pound",
+          "@root-docs", "@ruby-owner", "@space-owner"
+        ]
+
         where(:section, :patterns, :owners) do
-          "codeowners"    | ["/**/ee/**/*"] | ["@gl-admin"]
+          "codeowners"    | codeowners_section_paths | codeowners_section_owners
           "Documentation" | ["/**/README.md", "/**/ee/docs", "/**/docs"] | ["@gl-docs"]
           "Database"      | ["/**/README.md", "/**/model/db"] | ["@gl-database"]
         end
@@ -226,7 +239,7 @@ describe Gitlab::CodeOwners::File do
       end
 
       it 'correctly matches paths with spaces' do
-        entry = file.entry_for_path('path with spaces/README.md').first
+        entry = file.entry_for_path('path with spaces/docs.md').first
 
         expect(entry.owner_line).to eq('@space-owner')
       end
@@ -285,7 +298,17 @@ describe Gitlab::CodeOwners::File do
         stub_feature_flags(sectional_codeowners: true)
       end
 
-      it_behaves_like "returns expected matches"
+      context "when CODEOWNERS file contains no sections" do
+        it_behaves_like "returns expected matches"
+      end
+
+      context "when CODEOWNERS file contains multiple sections" do
+        let(:file_content) do
+          File.read(Rails.root.join("ee", "spec", "fixtures", "sectional_codeowners_example"))
+        end
+
+        it_behaves_like "returns expected matches"
+      end
     end
 
     context "when feature flag `:sectional_codeowners` is disabled" do
@@ -293,7 +316,17 @@ describe Gitlab::CodeOwners::File do
         stub_feature_flags(sectional_codeowners: false)
       end
 
-      it_behaves_like "returns expected matches"
+      context "when CODEOWNERS file contains no sections" do
+        it_behaves_like "returns expected matches"
+      end
+
+      context "when CODEOWNERS file contains multiple sections" do
+        let(:file_content) do
+          File.read(Rails.root.join("ee", "spec", "fixtures", "sectional_codeowners_example"))
+        end
+
+        it_behaves_like "returns expected matches"
+      end
     end
   end
 end