6 files changed, 152 insertions, 0 deletions
diff --git a/spec/fixtures/requests/oembed_invalid_xml.html b/spec/fixtures/requests/oembed_invalid_xml.html
new file mode 100644
index 000000000..405834f12
--- /dev/null
+++ b/spec/fixtures/requests/oembed_invalid_xml.html
@@ -0,0 +1,7 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <link href=':' rel='alternate' type='application/xml+oembed'>
+  </head>
+  <body></body>
+</html>
diff --git a/spec/fixtures/requests/oembed_json.html b/spec/fixtures/requests/oembed_json.html
new file mode 100644
index 000000000..773a4f92a
--- /dev/null
+++ b/spec/fixtures/requests/oembed_json.html
@@ -0,0 +1,7 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <link href='https://host/provider.json' rel='alternate' type='application/json+oembed'>
+  </head>
+  <body></body>
+</html>
diff --git a/spec/fixtures/requests/oembed_json_xml.html b/spec/fixtures/requests/oembed_json_xml.html
new file mode 100644
index 000000000..b5fc9bed0
--- /dev/null
+++ b/spec/fixtures/requests/oembed_json_xml.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <link href='https://host/provider.json' rel='alternate' type='application/json+oembed'>
+    <link href='https://host/provider.xml' rel='alternate' type='application/xml+oembed'>
+  </head>
+  <body></body>
+</html>
diff --git a/spec/fixtures/requests/oembed_undiscoverable.html b/spec/fixtures/requests/oembed_undiscoverable.html
new file mode 100644
index 000000000..a4acdc47a
--- /dev/null
+++ b/spec/fixtures/requests/oembed_undiscoverable.html
@@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<html>
+  <head></head>
+  <body></body>
+</html>
diff --git a/spec/fixtures/requests/oembed_xml.html b/spec/fixtures/requests/oembed_xml.html
new file mode 100644
index 000000000..5d7633e71
--- /dev/null
+++ b/spec/fixtures/requests/oembed_xml.html
@@ -0,0 +1,7 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <link href='https://host/provider.xml' rel='alternate' type='application/xml+oembed'>
+  </head>
+  <body></body>
+</html>
diff --git a/spec/lib/provider_discovery_spec.rb b/spec/lib/provider_discovery_spec.rb
new file mode 100644
index 000000000..12e2616c9
--- /dev/null
+++ b/spec/lib/provider_discovery_spec.rb
@@ -0,0 +1,118 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe ProviderDiscovery do
+  describe 'discover_provider' do
+    context 'when status code is 200 and MIME type is text/html' do
+      context 'Both of JSON and XML provider are discoverable' do
+        before do
+          stub_request(:get, 'https://host/oembed.html').to_return(
+            status: 200,
+            headers: { 'Content-Type': 'text/html' },
+            body: request_fixture('oembed_json_xml.html')
+          )
+        end
+
+        it 'returns new OEmbed::Provider for JSON provider if :format option is set to :json' do
+          provider = ProviderDiscovery.discover_provider('https://host/oembed.html', format: :json)
+          expect(provider.endpoint).to eq 'https://host/provider.json'
+          expect(provider.format).to eq :json
+        end
+
+        it 'returns new OEmbed::Provider for XML provider if :format option is set to :xml' do
+          provider = ProviderDiscovery.discover_provider('https://host/oembed.html', format: :xml)
+          expect(provider.endpoint).to eq 'https://host/provider.xml'
+          expect(provider.format).to eq :xml
+        end
+      end
+
+      context 'JSON provider is discoverable while XML provider is not' do
+        before do
+          stub_request(:get, 'https://host/oembed.html').to_return(
+            status: 200,
+            headers: { 'Content-Type': 'text/html' },
+            body: request_fixture('oembed_json.html')
+          )
+        end
+
+        it 'returns new OEmbed::Provider for JSON provider' do
+          provider = ProviderDiscovery.discover_provider('https://host/oembed.html')
+          expect(provider.endpoint).to eq 'https://host/provider.json'
+          expect(provider.format).to eq :json
+        end
+      end
+
+      context 'XML provider is discoverable while JSON provider is not' do
+        before do
+          stub_request(:get, 'https://host/oembed.html').to_return(
+            status: 200,
+            headers: { 'Content-Type': 'text/html' },
+            body: request_fixture('oembed_xml.html')
+          )
+        end
+
+        it 'returns new OEmbed::Provider for XML provider' do
+          provider = ProviderDiscovery.discover_provider('https://host/oembed.html')
+          expect(provider.endpoint).to eq 'https://host/provider.xml'
+          expect(provider.format).to eq :xml
+        end
+      end
+
+      context 'Invalid XML provider is discoverable while JSON provider is not' do
+        before do
+          stub_request(:get, 'https://host/oembed.html').to_return(
+            status: 200,
+            headers: { 'Content-Type': 'text/html' },
+            body: request_fixture('oembed_invalid_xml.html')
+          )
+        end
+
+        it 'raises OEmbed::NotFound' do
+          expect { ProviderDiscovery.discover_provider('https://host/oembed.html') }.to raise_error OEmbed::NotFound
+        end
+      end
+
+      context 'Neither of JSON and XML provider is discoverable' do
+        before do
+          stub_request(:get, 'https://host/oembed.html').to_return(
+            status: 200,
+            headers: { 'Content-Type': 'text/html' },
+            body: request_fixture('oembed_undiscoverable.html')
+          )
+        end
+
+        it 'raises OEmbed::NotFound' do
+          expect { ProviderDiscovery.discover_provider('https://host/oembed.html') }.to raise_error OEmbed::NotFound
+        end
+      end
+    end
+
+    context 'when status code is not 200' do
+      before do
+        stub_request(:get, 'https://host/oembed.html').to_return(
+          status: 400,
+          headers: { 'Content-Type': 'text/html' },
+          body: request_fixture('oembed_xml.html')
+        )
+      end
+
+      it 'raises OEmbed::NotFound' do
+        expect { ProviderDiscovery.discover_provider('https://host/oembed.html') }.to raise_error OEmbed::NotFound
+      end
+    end
+
+    context 'when MIME type is not text/html' do
+      before do
+        stub_request(:get, 'https://host/oembed.html').to_return(
+          status: 200,
+          body: request_fixture('oembed_xml.html')
+        )
+      end
+
+      it 'raises OEmbed::NotFound' do
+        expect { ProviderDiscovery.discover_provider('https://host/oembed.html') }.to raise_error OEmbed::NotFound
+      end
+    end
+  end
+end