GithubRelease: Add tests

This adds tests to cover all of the strategy outside of the
`#find_versions` method, which we don't currently test because it
involves a network request.

Library/Homebrew/test/livecheck/strategy/github_release_spec.rb

@@ -0,0 +1,157 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy"
+
+describe Homebrew::Livecheck::Strategy::GithubRelease do
+  subject(:github_release) { described_class }
+
+  let(:github_urls) do
+    {
+      release_artifact:  "https://github.com/abc/def/releases/download/1.2.3/ghi-1.2.3.tar.gz",
+      tag_archive:       "https://github.com/abc/def/archive/v1.2.3.tar.gz",
+      repository_upload: "https://github.com/downloads/abc/def/ghi-1.2.3.tar.gz",
+    }
+  end
+  let(:non_github_url) { "https://brew.sh/test" }
+
+  let(:regex) { github_release::DEFAULT_REGEX }
+
+  let(:generated) do
+    {
+      url:        "https://api.github.com/repos/abc/def/releases",
+      username:   "abc",
+      repository: "def",
+    }
+  end
+
+  # For the sake of brevity, this is a limited subset of the information found
+  # in release objects in a response from the GitHub API. Some of these objects
+  # are somewhat representative of real world scenarios but others are
+  # contrived examples for the sake of exercising code paths.
+  let(:content) do
+    <<~EOS
+      [
+        {
+          "tag_name": "v1.2.3",
+          "name": "v1.2.3",
+          "draft": false,
+          "prerelease": false
+        },
+        {
+          "tag_name": "no-version-tag-also",
+          "name": "1.2.2",
+          "draft": false,
+          "prerelease": false
+        },
+        {
+          "tag_name": "1.2.1",
+          "name": "No version title",
+          "draft": false,
+          "prerelease": false
+        },
+        {
+          "tag_name": "no-version-tag",
+          "name": "No version title",
+          "draft": false,
+          "prerelease": false
+        },
+        {
+          "tag_name": "v1.1.2",
+          "name": "v1.1.2",
+          "draft": false,
+          "prerelease": true
+        },
+        {
+          "tag_name": "v1.1.1",
+          "name": "v1.1.1",
+          "draft": true,
+          "prerelease": false
+        },
+        {
+          "tag_name": "v1.1.0",
+          "name": "v1.1.0",
+          "draft": true,
+          "prerelease": true
+        },
+        {
+          "other": "something-else"
+        }
+      ]
+    EOS
+  end
+  let(:json) { JSON.parse(content) }
+
+  let(:matches) { ["1.2.3", "1.2.2", "1.2.1"] }
+
+  describe "::match?" do
+    it "returns true for a GitHub release artifact URL" do
+      expect(github_release.match?(github_urls[:release_artifact])).to be true
+    end
+
+    it "returns true for a GitHub tag archive URL" do
+      expect(github_release.match?(github_urls[:tag_archive])).to be true
+    end
+
+    it "returns true for a GitHub repository upload URL" do
+      expect(github_release.match?(github_urls[:repository_upload])).to be true
+    end
+
+    it "returns false for a non-GitHub URL" do
+      expect(github_release.match?(non_github_url)).to be false
+    end
+  end
+
+  describe "::generate_input_values" do
+    it "returns a hash containing a url and regex for a GitHub release artifact URL" do
+      expect(github_release.generate_input_values(github_urls[:release_artifact])).to eq(generated)
+    end
+
+    it "returns a hash containing a url and regex for a GitHub tag archive URL" do
+      expect(github_release.generate_input_values(github_urls[:tag_archive])).to eq(generated)
+    end
+
+    it "returns a hash containing a url and regex for a GitHub repository upload URL" do
+      expect(github_release.generate_input_values(github_urls[:repository_upload])).to eq(generated)
+    end
+
+    it "returns an empty hash for a non-Github URL" do
+      expect(github_release.generate_input_values(non_github_url)).to eq({})
+    end
+  end
+
+  describe "::versions_from_content" do
+    it "returns an empty array if content is blank" do
+      expect(github_release.versions_from_content({}, regex)).to eq([])
+    end
+
+    it "returns an array of version strings when given content" do
+      expect(github_release.versions_from_content(json, regex)).to eq(matches)
+    end
+
+    it "returns an array of version strings when given content and a block" do
+      # Returning a string from block
+      expect(github_release.versions_from_content(json, regex) { "1.2.3" }).to eq(["1.2.3"])
+
+      # Returning an array of strings from block
+      expect(github_release.versions_from_content(json, regex) do |json, regex|
+        json.map do |release|
+          next if release["draft"] || release["prerelease"]
+
+          match = release["tag_name"]&.match(regex)
+          next if match.blank?
+
+          match[1]
+        end
+      end).to eq(["1.2.3", "1.2.1"])
+    end
+
+    it "allows a nil return from a block" do
+      expect(github_release.versions_from_content(json, regex) { next }).to eq([])
+    end
+
+    it "errors on an invalid return type from a block" do
+      expect { github_release.versions_from_content(json, regex) { 123 } }
+        .to raise_error(TypeError, Homebrew::Livecheck::Strategy::INVALID_BLOCK_RETURN_VALUE_MSG)
+    end
+  end
+end