diff --git a/Library/Homebrew/test/api/cask_spec.rb b/Library/Homebrew/test/api/cask_spec.rb
new file mode 100644
index 0000000000..35c561b8f9
--- /dev/null
+++ b/Library/Homebrew/test/api/cask_spec.rb
@@ -0,0 +1,44 @@
+# typed: false
+# frozen_string_literal: true
+
+require "api"
+
+describe Homebrew::API::Cask do
+  let(:cache_dir) { mktmpdir }
+
+  before do
+    stub_const("Homebrew::API::HOMEBREW_CACHE_API", cache_dir)
+  end
+
+  def mock_curl_download(stdout:)
+    allow(Utils::Curl).to receive(:curl_download) do |*_args, **kwargs|
+      kwargs[:to].write stdout
+    end
+  end
+
+  describe "::all_casks" do
+    let(:casks_json) {
+      <<~EOS
+        [{
+          "token": "foo",
+          "url": "https://brew.sh/foo"
+        }, {
+          "token": "bar",
+          "url": "https://brew.sh/bar"
+        }]
+      EOS
+    }
+    let(:casks_hash) {
+      {
+        "foo" => { "url" => "https://brew.sh/foo" },
+        "bar" => { "url" => "https://brew.sh/bar" },
+      }
+    }
+
+    it "returns the expected cask JSON list" do
+      mock_curl_download stdout: casks_json
+      casks_output = described_class.all_casks
+      expect(casks_output).to eq casks_hash
+    end
+  end
+end
diff --git a/Library/Homebrew/test/api/formula_spec.rb b/Library/Homebrew/test/api/formula_spec.rb
new file mode 100644
index 0000000000..38dbb57d5f
--- /dev/null
+++ b/Library/Homebrew/test/api/formula_spec.rb
@@ -0,0 +1,64 @@
+# typed: false
+# frozen_string_literal: true
+
+require "api"
+
+describe Homebrew::API::Formula do
+  let(:cache_dir) { mktmpdir }
+
+  before do
+    stub_const("Homebrew::API::HOMEBREW_CACHE_API", cache_dir)
+  end
+
+  def mock_curl_download(stdout:)
+    allow(Utils::Curl).to receive(:curl_download) do |*_args, **kwargs|
+      kwargs[:to].write stdout
+    end
+  end
+
+  describe "::all_formulae" do
+    let(:formulae_json) {
+      <<~EOS
+        [{
+          "name": "foo",
+          "url": "https://brew.sh/foo",
+          "aliases": ["foo-alias1", "foo-alias2"]
+        }, {
+          "name": "bar",
+          "url": "https://brew.sh/bar",
+          "aliases": ["bar-alias"]
+        }, {
+          "name": "baz",
+          "url": "https://brew.sh/baz",
+          "aliases": []
+        }]
+      EOS
+    }
+    let(:formulae_hash) {
+      {
+        "foo" => { "url" => "https://brew.sh/foo", "aliases" => ["foo-alias1", "foo-alias2"] },
+        "bar" => { "url" => "https://brew.sh/bar", "aliases" => ["bar-alias"] },
+        "baz" => { "url" => "https://brew.sh/baz", "aliases" => [] },
+      }
+    }
+    let(:formulae_aliases) {
+      {
+        "foo-alias1" => "foo",
+        "foo-alias2" => "foo",
+        "bar-alias"  => "bar",
+      }
+    }
+
+    it "returns the expected formula JSON list" do
+      mock_curl_download stdout: formulae_json
+      formulae_output = described_class.all_formulae
+      expect(formulae_output).to eq formulae_hash
+    end
+
+    it "returns the expected formula alias list" do
+      mock_curl_download stdout: formulae_json
+      aliases_output = described_class.all_aliases
+      expect(aliases_output).to eq formulae_aliases
+    end
+  end
+end
diff --git a/Library/Homebrew/test/api_spec.rb b/Library/Homebrew/test/api_spec.rb
index 6d70ef6626..ff695bfe77 100644
--- a/Library/Homebrew/test/api_spec.rb
+++ b/Library/Homebrew/test/api_spec.rb
@@ -7,12 +7,19 @@ describe Homebrew::API do
   let(:text) { "foo" }
   let(:json) { '{"foo":"bar"}' }
   let(:json_hash) { JSON.parse(json) }
+  let(:json_invalid) { '{"foo":"bar"' }
 
   def mock_curl_output(stdout: "", success: true)
     curl_output = OpenStruct.new(stdout: stdout, success?: success)
     allow(Utils::Curl).to receive(:curl_output).and_return curl_output
   end
 
+  def mock_curl_download(stdout:)
+    allow(Utils::Curl).to receive(:curl_download) do |*_args, **kwargs|
+      kwargs[:to].write stdout
+    end
+  end
+
   describe "::fetch" do
     it "fetches a text file" do
       mock_curl_output stdout: text
@@ -36,4 +43,31 @@ describe Homebrew::API do
       expect { described_class.fetch("baz.txt") }.to raise_error(ArgumentError, /Invalid JSON file/)
     end
   end
+
+  describe "::fetch_json_api_file" do
+    let!(:cache_dir) { mktmpdir }
+
+    before do
+      (cache_dir/"bar.json").write "tmp"
+    end
+
+    it "fetches a JSON file" do
+      mock_curl_download stdout: json
+      fetched_json = described_class.fetch_json_api_file("foo.json", target: cache_dir/"foo.json")
+      expect(fetched_json).to eq json_hash
+    end
+
+    it "updates an existing JSON file" do
+      mock_curl_download stdout: json
+      fetched_json = described_class.fetch_json_api_file("bar.json", target: cache_dir/"bar.json")
+      expect(fetched_json).to eq json_hash
+    end
+
+    it "raises an error if the JSON file is invalid" do
+      mock_curl_download stdout: json_invalid
+      expect {
+        described_class.fetch_json_api_file("baz.json", target: cache_dir/"baz.json")
+      }.to raise_error(SystemExit)
+    end
+  end
 end