diff --git a/src/spec.cr b/src/spec.cr
new file mode 100644
index 0000000..0599058
--- /dev/null
+++ b/src/spec.cr
@@ -0,0 +1,514 @@
+require "spec"
+
+private def assert_single_read(rs, value_type, value)
+  rs.move_next.should be_true
+  rs.read(value_type).should eq(value)
+  rs.move_next.should be_false
+end
+
+module DB
+  # Helper class to ensure behaviour of custom drivers
+  #
+  # ```
+  # require "db/spec"
+  #
+  # DB::DriverSpecs(DB::Any).run do
+  #   # How to connect to database
+  #   connection_string "scheme://database_url"
+  #
+  #   # Clean up database if needed using before/after callbacks
+  #   before do
+  #     # ...
+  #   end
+  #
+  #   after do
+  #     # ...
+  #   end
+  #
+  #   # Sample values that will be stored, retrieved across many specs
+  #   sample_value "hello", "varchar(25)", "'hello'"
+  #
+  #   it "custom spec with a db initialized" do |db|
+  #     # assert something using *db*
+  #   end
+  #
+  #   # Configure the appropiate syntax for different commands needed to run the specs
+  #   binding_syntax do |index|
+  #     "?"
+  #   end
+  #
+  #   create_table_1column_syntax do |table_name, col1|
+  #     "create table #{table_name} (#{col1.name} #{col1.sql_type} #{col1.null ? "NULL" : "NOT NULL"})"
+  #   end
+  # end
+  # ```
+  #
+  # The following methods needs to be called to configure the appropiate syntax
+  # for different commands and allow all the specs to run: `binding_syntax`, `create_table_1column_syntax`,
+  # `create_table_2columns_syntax`, `select_1column_syntax`, `select_2columns_syntax`, `select_count_syntax`,
+  # `select_scalar_syntax`, `insert_1column_syntax`, `insert_2columns_syntax`, `drop_table_if_exists_syntax`.
+  #
+  class DriverSpecs(DBAnyType)
+    record ColumnDef, name : String, sql_type : String, null : Bool
+
+    @before : Proc(Nil) = ->{}
+    @after : Proc(Nil) = ->{}
+    @encode_null = "NULL"
+    @support_prepared = true
+    @support_unprepared = true
+
+    def before(&@before : -> Nil)
+    end
+
+    def after(&@after : -> Nil)
+    end
+
+    def encode_null(@encode_null : String)
+    end
+
+    # Allow specs that uses prepared statements (default `true`)
+    def support_prepared(@support_prepared : Bool)
+    end
+
+    # :nodoc:
+    def support_prepared
+      @support_prepared
+    end
+
+    # Allow specs that uses unprepared statements (default `true`)
+    def support_unprepared(@support_unprepared : Bool)
+    end
+
+    # :nodoc:
+    def support_unprepared
+      @support_unprepared
+    end
+
+    # :nodoc:
+    macro db_spec_config(name, *, block = false)
+      {% if name.is_a?(TypeDeclaration) %}
+        @{{name.var.id}} : {{name.type}}?
+
+        {% if block %}
+          def {{name.var.id}}(&@{{name.var.id}} : {{name.type}})
+          end
+        {% else %}
+          def {{name.var.id}}(@{{name.var.id}} : {{name.type}})
+          end
+        {% end %}
+
+        # :nodoc:
+        def {{name.var.id}}
+          res = @{{name.var.id}}
+          raise "Missing {{name.var.id}} to setup db" unless res
+          res
+        end
+      {% end %}
+    end
+
+    db_spec_config connection_string : String
+    db_spec_config binding_syntax : Proc(Int32, String), block: true
+    db_spec_config select_scalar_syntax : Proc(String, String?, String), block: true
+    db_spec_config create_table_1column_syntax : Proc(String, ColumnDef, String), block: true
+    db_spec_config create_table_2columns_syntax : Proc(String, ColumnDef, ColumnDef, String), block: true
+    db_spec_config insert_1column_syntax : Proc(String, ColumnDef, String, String), block: true
+    db_spec_config insert_2columns_syntax : Proc(String, ColumnDef, String, ColumnDef, String, String), block: true
+    db_spec_config select_1column_syntax : Proc(String, ColumnDef, String), block: true
+    db_spec_config select_2columns_syntax : Proc(String, ColumnDef, ColumnDef, String), block: true
+    db_spec_config select_count_syntax : Proc(String, String), block: true
+    db_spec_config drop_table_if_exists_syntax : Proc(String, String), block: true
+
+    # :nodoc:
+    record SpecIt, description : String, prepared : Symbol, file : String, line : Int32, end_line : Int32, block : DB::Database -> Nil
+    getter its = [] of SpecIt
+
+    def it(description = "assert", prepared = :default, file = __FILE__, line = __LINE__, end_line = __END_LINE__, &block : DB::Database ->)
+      return unless Spec.matches?(description, file, line, end_line)
+      @its << SpecIt.new(description, prepared, file, line, end_line, block)
+    end
+
+    # :nodoc:
+    record ValueDef(T), value : T, sql_type : String, value_encoded : String
+
+    @values = [] of ValueDef(DBAnyType)
+
+    # Use *value* as sample value that should be stored in columns of type *sql_type*.
+    # *value_encoded* is driver specific expression that should generate that value in the database.
+    # *type_safe_value* indicates whether *value_encoded* is expected to generate the *value* even without
+    # been stored in a table (default `true`).
+    def sample_value(value, sql_type, value_encoded, *, type_safe_value = true)
+      @values << ValueDef(DBAnyType).new(value, sql_type, value_encoded)
+
+      it "select nil as (#{typeof(value)} | Nil)", prepared: :both do |db|
+        db.query select_scalar(encode_null, nil) do |rs|
+          assert_single_read rs, typeof(value || nil), nil
+        end
+      end
+
+      value_desc = value.to_s
+      value_desc = "#{value_desc[0..25]}...(#{value_desc.size})" if value_desc.size > 25
+      value_desc = "#{value_desc} as #{sql_type}"
+
+      if type_safe_value
+        it "executes with bind #{value_desc}" do |db|
+          db.scalar(select_scalar(param(1), sql_type), value).should eq(value)
+        end
+
+        it "executes with bind #{value_desc} as array" do |db|
+          db.scalar(select_scalar(param(1), sql_type), [value]).should eq(value)
+        end
+
+        it "select #{value_desc} as literal" do |db|
+          db.scalar(select_scalar(value_encoded, sql_type)).should eq(value)
+
+          db.query select_scalar(value_encoded, sql_type) do |rs|
+            assert_single_read rs, typeof(value), value
+          end
+        end
+      end
+
+      it "insert/get value #{value_desc} from table", prepared: :both do |db|
+        db.exec sql_create_table_table1(c1 = col1(sql_type))
+        db.exec sql_insert_table1(c1, value_encoded)
+
+        db.query_one(sql_select_table1(c1), as: typeof(value)).should eq(value)
+      end
+
+      it "insert/get value #{value_desc} from table as nillable", prepared: :both do |db|
+        db.exec sql_create_table_table1(c1 = col1(sql_type))
+        db.exec sql_insert_table1(c1, value_encoded)
+
+        db.query_one(sql_select_table1(c1), as: ::Union(typeof(value) | Nil)).should eq(value)
+      end
+
+      it "insert/get value nil from table as nillable #{sql_type}", prepared: :both do |db|
+        db.exec sql_create_table_table1(c1 = col1(sql_type, null: true))
+        db.exec sql_insert_table1(c1, encode_null)
+
+        db.query_one(sql_select_table1(c1), as: ::Union(typeof(value) | Nil)).should eq(nil)
+      end
+
+      it "insert/get value #{value_desc} from table with binding" do |db|
+        db.exec sql_create_table_table2(c1 = col1(sql_type_for(String)), c2 = col2(sql_type))
+        # the next statement will force a union in the *args
+        db.exec sql_insert_table2(c1, param(1), c2, param(2)), value_for(String), value
+        db.query_one(sql_select_table2(c2), as: typeof(value)).should eq(value)
+      end
+
+      it "insert/get value #{value_desc} from table as nillable with binding" do |db|
+        db.exec sql_create_table_table2(c1 = col1(sql_type_for(String)), c2 = col2(sql_type))
+        # the next statement will force a union in the *args
+        db.exec sql_insert_table2(c1, param(1), c2, param(2)), value_for(String), value
+        db.query_one(sql_select_table2(c2), as: ::Union(typeof(value) | Nil)).should eq(value)
+      end
+
+      it "insert/get value nil from table as nillable #{sql_type} with binding" do |db|
+        db.exec sql_create_table_table2(c1 = col1(sql_type_for(String)), c2 = col2(sql_type, null: true))
+        db.exec sql_insert_table2(c1, param(1), c2, param(2)), value_for(String), nil
+
+        db.query_one(sql_select_table2(c2), as: ::Union(typeof(value) | Nil)).should eq(nil)
+      end
+
+      it "can use read(#{typeof(value)}) with DB::ResultSet", prepared: :both do |db|
+        db.exec sql_create_table_table1(c1 = col1(sql_type))
+        db.exec sql_insert_table1(c1, value_encoded)
+        db.query(sql_select_table1(c1)) do |rs|
+          assert_single_read rs.as(DB::ResultSet), typeof(value), value
+        end
+      end
+
+      it "can use read(#{typeof(value)}?) with DB::ResultSet", prepared: :both do |db|
+        db.exec sql_create_table_table1(c1 = col1(sql_type))
+        db.exec sql_insert_table1(c1, value_encoded)
+        db.query(sql_select_table1(c1)) do |rs|
+          assert_single_read rs.as(DB::ResultSet), ::Union(typeof(value) | Nil), value
+        end
+      end
+
+      it "can use read(#{typeof(value)}?) with DB::ResultSet for nil", prepared: :both do |db|
+        db.exec sql_create_table_table1(c1 = col1(sql_type, null: true))
+        db.exec sql_insert_table1(c1, encode_null)
+        db.query(sql_select_table1(c1)) do |rs|
+          assert_single_read rs.as(DB::ResultSet), ::Union(typeof(value) | Nil), nil
+        end
+      end
+    end
+
+    # :nodoc:
+    def include_shared_specs
+      it "connects using connection_string" do |db|
+        db.is_a?(DB::Database)
+      end
+
+      it "can create direct connection" do
+        DB.connect(connection_string) do |cnn|
+          cnn.is_a?(DB::Connection)
+          cnn.scalar(select_scalar(encode_null, nil)).should be_nil
+        end
+      end
+
+      it "binds nil" do |db|
+        # PG is unable to perform this query without a type annotation
+        db.scalar(select_scalar(param(1), sql_type_for(String)), nil).should be_nil
+      end
+
+      it "selects nil as scalar", prepared: :both do |db|
+        db.scalar(select_scalar(encode_null, nil)).should be_nil
+      end
+
+      it "gets column count", prepared: :both do |db|
+        db.exec sql_create_table_person
+        db.query "select * from person" do |rs|
+          rs.column_count.should eq(2)
+        end
+      end
+
+      it "gets column name", prepared: :both do |db|
+        db.exec sql_create_table_person
+
+        db.query "select name, age from person" do |rs|
+          rs.column_name(0).should eq("name")
+          rs.column_name(1).should eq("age")
+        end
+      end
+
+      it "gets many rows from table" do |db|
+        db.exec sql_create_table_person
+        db.exec sql_insert_person, "foo", 10
+        db.exec sql_insert_person, "bar", 20
+        db.exec sql_insert_person, "baz", 30
+
+        names = [] of String
+        ages = [] of Int32
+        db.query sql_select_person do |rs|
+          rs.each do
+            names << rs.read(String)
+            ages << rs.read(Int32)
+          end
+        end
+        names.should eq(["foo", "bar", "baz"])
+        ages.should eq([10, 20, 30])
+      end
+
+      # describe "transactions" do
+      it "transactions: can read inside transaction and rollback after" do |db|
+        db.exec sql_create_table_person
+        db.transaction do |tx|
+          tx.connection.scalar(sql_select_count_person).should eq(0)
+          tx.connection.exec sql_insert_person, "John Doe", 10
+          tx.connection.scalar(sql_select_count_person).should eq(1)
+          tx.rollback
+        end
+        db.scalar(sql_select_count_person).should eq(0)
+      end
+
+      it "transactions: can read inside transaction or after commit" do |db|
+        db.exec sql_create_table_person
+        db.transaction do |tx|
+          tx.connection.scalar(sql_select_count_person).should eq(0)
+          tx.connection.exec sql_insert_person, "John Doe", 10
+          tx.connection.scalar(sql_select_count_person).should eq(1)
+          # using other connection
+          db.scalar(sql_select_count_person).should eq(0)
+        end
+        db.scalar("select count(*) from person").should eq(1)
+      end
+      # end
+
+      # describe "nested transactions" do
+      it "nested transactions: can read inside transaction and rollback after" do |db|
+        db.exec sql_create_table_person
+        db.transaction do |tx_0|
+          tx_0.connection.scalar(sql_select_count_person).should eq(0)
+          tx_0.connection.exec sql_insert_person, "John Doe", 10
+          tx_0.transaction do |tx_1|
+            tx_1.connection.exec sql_insert_person, "Sarah", 11
+            tx_1.connection.scalar(sql_select_count_person).should eq(2)
+            tx_1.transaction do |tx_2|
+              tx_2.connection.exec sql_insert_person, "Jimmy", 12
+              tx_2.connection.scalar(sql_select_count_person).should eq(3)
+              tx_2.rollback
+            end
+          end
+          tx_0.connection.scalar(sql_select_count_person).should eq(2)
+          tx_0.rollback
+        end
+        db.scalar(sql_select_count_person).should eq(0)
+      end
+      # end
+    end
+
+    # :nodoc:
+    def with_db(options = nil)
+      @before.call
+      DB.open("#{connection_string}#{"?#{options}" if options}") do |db|
+        db.exec(sql_drop_table("table1"))
+        db.exec(sql_drop_table("table2"))
+        db.exec(sql_drop_table("person"))
+        yield db
+      end
+    ensure
+      @after.call
+    end
+
+    # :nodoc:
+    def select_scalar(expression, sql_type)
+      select_scalar_syntax.call(expression, sql_type)
+    end
+
+    # :nodoc:
+    def param(index)
+      binding_syntax.call(index)
+    end
+
+    # :nodoc:
+    def encode_null
+      @encode_null
+    end
+
+    # :nodoc:
+    def sql_type_for(a_class)
+      value = @values.select { |v| v.value.class == a_class }.first?
+      if value
+        value.sql_type
+      else
+        raise "missing sample_value with #{a_class}"
+      end
+    end
+
+    # :nodoc:
+    macro value_for(a_class)
+      _value_for({{a_class}}).as({{a_class}})
+    end
+
+    # :nodoc:
+    def _value_for(a_class)
+      value = @values.select { |v| v.value.class == a_class }.first?
+      if value
+        value.value
+      else
+        raise "missing sample_value with #{a_class}"
+      end
+    end
+
+    # :nodoc:
+    def col_name
+      ColumnDef.new("name", sql_type_for(String), false)
+    end
+
+    # :nodoc:
+    def col_age
+      ColumnDef.new("age", sql_type_for(Int32), false)
+    end
+
+    # :nodoc:
+    def sql_create_table_person
+      create_table_2columns_syntax.call("person", col_name, col_age)
+    end
+
+    # :nodoc:
+    def sql_select_person
+      select_2columns_syntax.call("person", col_name, col_age)
+    end
+
+    # :nodoc:
+    def sql_insert_person
+      insert_2columns_syntax.call("person", col_name, param(1), col_age, param(2))
+    end
+
+    # :nodoc:
+    def sql_select_count_person
+      select_count_syntax.call("person")
+    end
+
+    # :nodoc:
+    def col1(sql_type, *, null = false)
+      ColumnDef.new("col1", sql_type, null)
+    end
+
+    # :nodoc:
+    def col2(sql_type, *, null = false)
+      ColumnDef.new("col2", sql_type, null)
+    end
+
+    # :nodoc:
+    def sql_create_table_table1(col : ColumnDef)
+      create_table_1column_syntax.call("table1", col)
+    end
+
+    # :nodoc:
+    def sql_create_table_table2(col1 : ColumnDef, col2 : ColumnDef)
+      create_table_2columns_syntax.call("table2", col1, col2)
+    end
+
+    # :nodoc:
+    def sql_insert_table1(col1 : ColumnDef, expression)
+      insert_1column_syntax.call("table1", col1, expression)
+    end
+
+    # :nodoc:
+    def sql_insert_table2(col1 : ColumnDef, expr1, col2 : ColumnDef, expr2)
+      insert_2columns_syntax.call("table2", col1, expr1, col2, expr2)
+    end
+
+    # :nodoc:
+    def sql_select_table1(col : ColumnDef)
+      select_1column_syntax.call("table1", col)
+    end
+
+    # :nodoc:
+    def sql_select_table2(col : ColumnDef)
+      select_1column_syntax.call("table2", col)
+    end
+
+    # :nodoc:
+    def sql_drop_table(table_name)
+      drop_table_if_exists_syntax.call(table_name)
+    end
+
+    def self.run(description = "as a db")
+      ctx = self.new
+      with ctx yield
+
+      describe description do
+        ctx.include_shared_specs
+
+        ctx.its.each do |db_it|
+          case db_it.prepared
+          when :default
+            it(db_it.description, db_it.file, db_it.line, db_it.end_line) do
+              ctx.with_db do |db|
+                db_it.block.call db
+                nil
+              end
+            end
+          when :both
+            values = [] of Bool
+            values << true if ctx.support_prepared
+            values << false if ctx.support_unprepared
+            case values.size
+            when 0
+              raise "Neither prepared non unprepared statements allowed"
+            when 1
+              it(db_it.description, db_it.file, db_it.line, db_it.end_line) do
+                ctx.with_db do |db|
+                  db_it.block.call db
+                  nil
+                end
+              end
+            else
+              values.each do |prepared_statements|
+                it("#{db_it.description} (prepared_statements=#{prepared_statements})", db_it.file, db_it.line, db_it.end_line) do
+                  ctx.with_db "prepared_statements=#{prepared_statements}" do |db|
+                    db_it.block.call db
+                    nil
+                  end
+                end
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end