add simple grammar rules and tests for simple cases

spec/query_parser_spec.rb

@@ -5,5 +5,31 @@ class QueryParserTester
     before do
       @evaluator = Query.new
     end
+
+    it 'tests query with only one search term without quotes and without column name' do
+      @result = @evaluator.parse('-123')
+
+      expect(@result[:DEFAULT_COLUMN]).to eq '-123'
+    end
+
+    it 'tests query with only one search term with quotes and without column name' do
+      @result = @evaluator.parse('"OR 128"')
+
+      expect(@result[:DEFAULT_COLUMN]).to eq '"OR 128"'
+    end
+
+    it 'tests query with one column and search term without quotes' do
+      @result = @evaluator.parse('tag:mta')
+
+      expect(@result['tag']).to eq 'mta'
+    end
+
+    it 'tests query with one column and search term with quotes' do
+      @result = @evaluator.parse('tag:"tag 120"')
+
+      expect(@result['tag']).to eq '"tag 120"'
+    end
+
+
   end
 end