diff --git a/configio/converters.go b/configio/converters.go
new file mode 100644
index 0000000..847dbc2
--- /dev/null
+++ b/configio/converters.go
@@ -0,0 +1,133 @@
+package configio
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+
+	"github.com/benchttp/engine/benchttp"
+)
+
+type (
+	converter        func(representation, *benchttp.Runner) error
+	requestConverter func(representation, *http.Request) error
+)
+
+var fieldConverters = []converter{
+	func(repr representation, dst *benchttp.Runner) error {
+		req := dst.Request
+		if req == nil {
+			req = &http.Request{}
+		}
+		for _, p := range requestConverters {
+			if err := p(repr, req); err != nil {
+				return err
+			}
+		}
+		dst.Request = req
+		return nil
+	},
+	func(repr representation, dst *benchttp.Runner) error {
+		for _, p := range runnerParsers {
+			if err := p(repr, dst); err != nil {
+				return err
+			}
+		}
+		return nil
+	},
+}
+
+var requestParser = func(repr representation, dst *benchttp.Runner) error {
+	req := &http.Request{}
+	for _, fieldParser := range requestConverters {
+		if err := fieldParser(repr, req); err != nil {
+			return err
+		}
+	}
+	dst.Request = req
+	return nil
+}
+
+var requestConverters = []requestConverter{
+	func(repr representation, dst *http.Request) error {
+		return setString(repr.Request.Method, &dst.Method)
+	},
+	func(repr representation, dst *http.Request) error {
+		if rawURL := repr.Request.URL; rawURL != nil {
+			parsedURL, err := parseAndBuildURL(*rawURL, repr.Request.QueryParams)
+			if err != nil {
+				return fmt.Errorf(`configio: invalid url: %q`, *rawURL)
+			}
+			dst.URL = parsedURL
+		}
+		return nil
+	},
+	func(repr representation, dst *http.Request) error {
+		if header := repr.Request.Header; len(header) != 0 {
+			httpHeader := http.Header{}
+			for key, val := range header {
+				httpHeader[key] = val
+			}
+			dst.Header = httpHeader
+		}
+		return nil
+	},
+	func(repr representation, dst *http.Request) error {
+		if body := repr.Request.Body; body != nil {
+			switch body.Type {
+			case "raw":
+				dst.Body = io.NopCloser(bytes.NewReader([]byte(body.Content)))
+			default:
+				return errors.New(`configio: request.body.type: only "raw" accepted`)
+			}
+		}
+		return nil
+	},
+}
+
+var runnerParsers = map[string]converter{
+	"requests": func(repr representation, dst *benchttp.Runner) error {
+		return setInt(repr.Runner.Requests, &dst.Requests)
+	},
+	"concurrency": func(repr representation, dst *benchttp.Runner) error {
+		return setInt(repr.Runner.Concurrency, &dst.Concurrency)
+	},
+	"interval": func(repr representation, dst *benchttp.Runner) error {
+		return setOptionalDuration(repr.Runner.Interval, &dst.Interval)
+	},
+	"requestTimeout": func(repr representation, dst *benchttp.Runner) error {
+		return setOptionalDuration(repr.Runner.RequestTimeout, &dst.RequestTimeout)
+	},
+	"globalTimeout": func(repr representation, dst *benchttp.Runner) error {
+		return setOptionalDuration(repr.Runner.GlobalTimeout, &dst.GlobalTimeout)
+	},
+}
+
+func setInt(src, dst *int) error {
+	if src != nil {
+		*dst = *src
+	}
+	return nil
+}
+
+func setString(src, dst *string) error {
+	if src != nil {
+		*dst = *src
+	}
+	return nil
+}
+
+func setOptionalDuration(src *string, dst *time.Duration) error {
+	if src == nil {
+		return nil
+	}
+	parsed, err := parseOptionalDuration(*src)
+	if err != nil {
+		return err
+	}
+	*dst = parsed
+	return nil
+}
diff --git a/configio/representation.go b/configio/representation.go
index bf851a1..76a0fc6 100644
--- a/configio/representation.go
+++ b/configio/representation.go
@@ -1,11 +1,7 @@
 package configio
 
 import (
-	"bytes"
-	"errors"
 	"fmt"
-	"io"
-	"net/http"
 	"net/url"
 	"strconv"
 	"time"
@@ -57,86 +53,13 @@ func (repr representation) validate() error {
 // and stores any non-nil field value into the corresponding field
 // of dst.
 func (repr representation) parseAndMutate(dst *benchttp.Runner) error {
-	if err := repr.parseRequestInto(dst); err != nil {
-		return err
-	}
-	if err := repr.parseRunnerInto(dst); err != nil {
-		return err
-	}
-	return repr.parseTestsInto(dst)
-}
-
-func (repr representation) parseRequestInto(dst *benchttp.Runner) error {
-	if dst.Request == nil {
-		dst.Request = &http.Request{}
-	}
-
-	if method := repr.Request.Method; method != nil {
-		dst.Request.Method = *method
-	}
-
-	if rawURL := repr.Request.URL; rawURL != nil {
-		parsedURL, err := parseAndBuildURL(*rawURL, repr.Request.QueryParams)
-		if err != nil {
-			return fmt.Errorf(`configio: invalid url: %q`, *rawURL)
-		}
-		dst.Request.URL = parsedURL
-	}
-
-	if header := repr.Request.Header; len(header) != 0 {
-		httpHeader := http.Header{}
-		for key, val := range header {
-			httpHeader[key] = val
-		}
-		dst.Request.Header = httpHeader
-	}
-
-	if body := repr.Request.Body; body != nil {
-		switch body.Type {
-		case "raw":
-			dst.Request.Body = io.NopCloser(bytes.NewReader([]byte(body.Content)))
-		default:
-			return errors.New(`configio: request.body.type: only "raw" accepted`)
-		}
-	}
-
-	return nil
-}
-
-func (repr representation) parseRunnerInto(dst *benchttp.Runner) error {
-	if requests := repr.Runner.Requests; requests != nil {
-		dst.Requests = *requests
-	}
-
-	if concurrency := repr.Runner.Concurrency; concurrency != nil {
-		dst.Concurrency = *concurrency
-	}
-
-	if interval := repr.Runner.Interval; interval != nil {
-		parsedInterval, err := parseOptionalDuration(*interval)
-		if err != nil {
-			return err
-		}
-		dst.Interval = parsedInterval
-	}
-
-	if requestTimeout := repr.Runner.RequestTimeout; requestTimeout != nil {
-		parsedTimeout, err := parseOptionalDuration(*requestTimeout)
-		if err != nil {
-			return err
-		}
-		dst.RequestTimeout = parsedTimeout
-	}
-
-	if globalTimeout := repr.Runner.GlobalTimeout; globalTimeout != nil {
-		parsedGlobalTimeout, err := parseOptionalDuration(*globalTimeout)
-		if err != nil {
+	for _, converter := range fieldConverters {
+		if err := converter(repr, dst); err != nil {
 			return err
 		}
-		dst.GlobalTimeout = parsedGlobalTimeout
 	}
-
-	return nil
+	// TODO: use converter for tests
+	return repr.parseTestsInto(dst)
 }
 
 func (repr representation) parseTestsInto(dst *benchttp.Runner) error {