added compile option

program.go

@@ -1,22 +1,21 @@
 package wrapper
 
 import (
+	"errors"
 	"fmt"
 	"os/exec"
 )
 
 type Program struct {
-	executable            string
-	params                map[string]interface{}
-	getCombinedOutputFunc func(cmd *exec.Cmd) ([]byte, error)
+	executable string
+	params     map[string]interface{}
 }
 
 func NewProgram(executable string) *Program {
 	program := &Program{
 		executable: executable,
 		params:     make(map[string]interface{}),
 	}
-	program.getCombinedOutputFunc = program.getCombinedOutput
 	return program
 }
 
@@ -25,7 +24,9 @@ func (p *Program) WithParam(name string, value interface{}) *Program {
 	return p
 }
 
-func (p *Program) getCombinedOutput(cmd *exec.Cmd) ([]byte, error) {
+var getCombinedOutputFunc = getCombinedOutput
+
+func getCombinedOutput(cmd *exec.Cmd) ([]byte, error) {
 	return cmd.CombinedOutput()
 }
 
@@ -37,9 +38,22 @@ func (p *Program) Run() (string, error) {
 	}
 
 	cmd := exec.Command(p.executable, params...)
-	output, err := p.getCombinedOutputFunc(cmd)
+	output, err := getCombinedOutputFunc(cmd)
 	if err != nil {
 		return "", err
 	}
 	return string(output), nil
 }
+
+func (p *Program) Compile(mainPath string) error {
+	cmd := exec.Command("go", "build", "-o", p.executable, mainPath)
+	output, err := getCombinedOutputFunc(cmd)
+	if err != nil {
+		return err
+	}
+	outputStr := string(output)
+	if outputStr != "" {
+		return errors.New("Error compiling: " + outputStr)
+	}
+	return nil
+}

program_test.go

@@ -0,0 +1,22 @@
+package wrapper
+
+import (
+	"errors"
+	"os/exec"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func Test_program_cmdError(t *testing.T) {
+
+	cmdErr := errors.New("test error")
+
+	program := NewProgram("")
+	getCombinedOutputFunc = func(cmd *exec.Cmd) ([]byte, error) {
+		return nil, cmdErr
+	}
+	defer func() { getCombinedOutputFunc = getCombinedOutput }()
+	_, err := program.Run()
+	require.Equal(t, cmdErr, err)
+}

test/program_test.go

@@ -29,6 +29,9 @@ func Test_program(t *testing.T) {
 	path := filepath.Join(wd, "../testProgram.exe")
 
 	program := wrapper.NewProgram(path)
+	err = program.Compile("../testProgram/main.go")
+	require.NoError(t, err)
+
 	output, err := program.Run()
 	require.NoError(t, err)
 	require.Contains(t, output, "default message")