1 files changed, 76 insertions, 0 deletions
diff --git a/activerecord/test/cases/explain_test.rb b/activerecord/test/cases/explain_test.rb
new file mode 100644
index 0000000000..9d25bdd82a
--- /dev/null
+++ b/activerecord/test/cases/explain_test.rb
@@ -0,0 +1,76 @@
+require 'cases/helper'
+require 'models/car'
+require 'active_support/core_ext/string/strip'
+
+if ActiveRecord::Base.connection.supports_explain?
+  class ExplainTest < ActiveRecord::TestCase
+    fixtures :cars
+
+    def base
+      ActiveRecord::Base
+    end
+
+    def connection
+      base.connection
+    end
+
+    def test_relation_explain
+      message = Car.where(:name => 'honda').explain
+      assert_match(/^EXPLAIN for:/, message)
+    end
+
+    def test_collecting_queries_for_explain
+      queries = ActiveRecord::Base.collecting_queries_for_explain do
+        Car.where(:name => 'honda').to_a
+      end
+
+      sql, binds = queries[0]
+      assert_match "SELECT", sql
+      if binds.any?
+        assert_equal 1, binds.length
+        assert_equal "honda", binds.flatten.last
+      else
+        assert_match 'honda', sql
+      end
+    end
+
+    def test_exec_explain_with_no_binds
+      sqls    = %w(foo bar)
+      binds   = [[], []]
+      queries = sqls.zip(binds)
+
+      connection.stubs(:explain).returns('query plan foo', 'query plan bar')
+      expected = sqls.map {|sql| "EXPLAIN for: #{sql}\nquery plan #{sql}"}.join("\n")
+      assert_equal expected, base.exec_explain(queries)
+    end
+
+    def test_exec_explain_with_binds
+      cols = [Object.new, Object.new]
+      cols[0].expects(:name).returns('wadus')
+      cols[1].expects(:name).returns('chaflan')
+
+      sqls    = %w(foo bar)
+      binds   = [[[cols[0], 1]], [[cols[1], 2]]]
+      queries = sqls.zip(binds)
+
+      connection.stubs(:explain).returns("query plan foo\n", "query plan bar\n")
+      expected = <<-SQL.strip_heredoc
+        EXPLAIN for: #{sqls[0]} [["wadus", 1]]
+        query plan foo
+
+        EXPLAIN for: #{sqls[1]} [["chaflan", 2]]
+        query plan bar
+      SQL
+      assert_equal expected, base.exec_explain(queries)
+    end
+
+    def test_unsupported_connection_adapter
+      connection.stubs(:supports_explain?).returns(false)
+
+      base.logger.expects(:warn).never
+
+      Car.where(:name => 'honda').to_a
+    end
+
+  end
+end