diff --git a/_tests/configurations/timeout-gotenberg.yml b/_tests/configurations/timeout-gotenberg.yml
new file mode 100644
index 00000000..99e24e5b
--- /dev/null
+++ b/_tests/configurations/timeout-gotenberg.yml
@@ -0,0 +1,14 @@
+port: 3000
+logs:
+  level: "DEBUG"
+  format: "text"
+commands:
+  html:
+    timeout: 0
+    template: "xvfb-run -e /dev/stdout wkhtmltopdf {{ .FilePath }} {{ .ResultFilePath }}"
+  office:
+    timeout: 0
+    template: "unoconv --format pdf --output \"{{ .ResultFilePath }}\" \"{{ .FilePath }}\""
+  merge:
+    timeout: 0
+    template: "pdftk {{ range $filePath := .FilesPaths }} {{ $filePath }} {{ end }} cat output {{ .ResultFilePath }}"
diff --git a/app/converter/process/process.go b/app/converter/process/process.go
index d2842cc4..dc127eba 100644
--- a/app/converter/process/process.go
+++ b/app/converter/process/process.go
@@ -27,8 +27,10 @@ type conversionData struct {
 
 type impossibleConversionError struct{}
 
+const impossibleConversionErrorMessage = "Impossible conversion"
+
 func (e *impossibleConversionError) Error() string {
-	return "Impossible conversion"
+	return impossibleConversionErrorMessage
 }
 
 // Unconv converts a file to PDF and returns the new file path.
@@ -100,8 +102,10 @@ func Merge(workingDir string, filesPaths []string) (string, error) {
 
 type commandTimeoutError struct{}
 
+const commandTimeoutErrorMessage = "The command has reached timeout"
+
 func (e *commandTimeoutError) Error() string {
-	return "The command has reached timeout"
+	return commandTimeoutErrorMessage
 }
 
 // run runs the given command. If timeout is reached or
diff --git a/app/converter/process/process_test.go b/app/converter/process/process_test.go
new file mode 100644
index 00000000..c597de89
--- /dev/null
+++ b/app/converter/process/process_test.go
@@ -0,0 +1,130 @@
+package process
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/gulien/gotenberg/app/config"
+	gfile "github.com/gulien/gotenberg/app/converter/file"
+)
+
+func TestLoad(t *testing.T) {
+	path, _ := filepath.Abs("../../../_tests/configurations/gotenberg.yml")
+	c, _ := config.NewAppConfig(path)
+	Load(c.CommandsConfig)
+
+	if c.CommandsConfig != commandsConfig {
+		t.Error("Commands configuration should have loaded correctly!")
+	}
+}
+
+func TestUnconv(t *testing.T) {
+	path, _ := filepath.Abs("../../../_tests/configurations/gotenberg.yml")
+	c, _ := config.NewAppConfig(path)
+	Load(c.CommandsConfig)
+
+	workingDir := "test"
+	os.Mkdir(workingDir, 0666)
+
+	// case 1: uses an HTML file type.
+	path, _ = filepath.Abs("../../../_tests/file.html")
+	r, _ := os.Open(path)
+	defer r.Close()
+	f, _ := gfile.NewFile(workingDir, r)
+	if _, err := Unconv(workingDir, f); err != nil {
+		t.Error("HTML conversion to PDF should have worked!")
+	}
+
+	// case 2: uses an Office file type.
+	path, _ = filepath.Abs("../../../_tests/file.docx")
+	r, _ = os.Open(path)
+	defer r.Close()
+	f, _ = gfile.NewFile(workingDir, r)
+	if _, err := Unconv(workingDir, f); err != nil {
+		t.Error("Office conversion to PDF should have worked!")
+	}
+
+	// case 3: uses a PDF file type.
+	path, _ = filepath.Abs("../../../_tests/file.pdf")
+	r, _ = os.Open(path)
+	defer r.Close()
+	f, _ = gfile.NewFile(workingDir, r)
+	if _, err := Unconv(workingDir, f); err == nil {
+		t.Error("PDF conversion to PDF should not have worked!")
+	}
+
+	// case 4: uses a command with an unsuitable timeout.
+	path, _ = filepath.Abs("../../../_tests/configurations/timeout-gotenberg.yml")
+	c, _ = config.NewAppConfig(path)
+	Load(c.CommandsConfig)
+	path, _ = filepath.Abs("../../../_tests/file.docx")
+	r, _ = os.Open(path)
+	defer r.Close()
+	f, _ = gfile.NewFile(workingDir, r)
+	if _, err := Unconv(workingDir, f); err == nil {
+		t.Error("Office conversion to PDF should have reached timeout!")
+	}
+
+	os.RemoveAll(workingDir)
+}
+
+func TestMerge(t *testing.T) {
+	path, _ := filepath.Abs("../../../_tests/configurations/gotenberg.yml")
+	c, _ := config.NewAppConfig(path)
+	Load(c.CommandsConfig)
+
+	workingDir := "test"
+	os.Mkdir(workingDir, 0666)
+
+	var filesPaths []string
+	path, _ = filepath.Abs("../../../_tests/file.pdf")
+	filesPaths = append(filesPaths, path)
+	filesPaths = append(filesPaths, path)
+
+	// case 1: simple merge.
+	if _, err := Merge(workingDir, filesPaths); err != nil {
+		t.Error("Merge should have worked!")
+	}
+
+	// case 2: uses a command with an unsuitable timeout.
+	path, _ = filepath.Abs("../../../_tests/configurations/timeout-gotenberg.yml")
+	c, _ = config.NewAppConfig(path)
+	Load(c.CommandsConfig)
+	if _, err := Merge(workingDir, filesPaths); err == nil {
+		t.Error("Merge should have reached timeout!")
+	}
+
+	os.RemoveAll(workingDir)
+}
+
+func TestRun(t *testing.T) {
+	// case 1: uses a simple command.
+	if err := run("echo Hello world", 30); err != nil {
+		t.Error("Command should have worked!")
+	}
+
+	// case 2: uses a simple command but with an unsuitable timeout.
+	if err := run("echo Hello world", 0); err == nil {
+		t.Error("Command should not have worked!")
+	}
+
+	// case 3: uses a broken command.
+	if err := run("helloworld", 30); err == nil {
+		t.Error("Command should not have worked!")
+	}
+}
+
+func TestImpossibleConversionError(t *testing.T) {
+	err := &impossibleConversionError{}
+	if err.Error() != impossibleConversionErrorMessage {
+		t.Errorf("Error returned a wrong message: got %s want %s", err.Error(), impossibleConversionErrorMessage)
+	}
+}
+
+func TestCommandTimeoutError(t *testing.T) {
+	err := &commandTimeoutError{}
+	if err.Error() != commandTimeoutErrorMessage {
+		t.Errorf("Error returned a wrong message: got %s want %s", err.Error(), commandTimeoutErrorMessage)
+	}
+}