added some more test coverage to fold subpackage. (#436)

fold/fold_test.go

@@ -1,6 +1,7 @@
 package fold
 
 import (
+	"fmt"
 	"math"
 	"strings"
 	"testing"
@@ -201,3 +202,13 @@ func TestFold(t *testing.T) {
 		assert.InDelta(t, struc.energy, -4.2, 0.2)
 	})
 }
+func TestZuker_ErrorCreatingFoldingContext(t *testing.T) {
+	seq := "ATGGATTTAGATAGATADFQ#(RSDOFIA)"
+	temp := 4000.0
+
+	expectedErr := fmt.Errorf("error creating folding context: the sequence ATGGATTTAGATAGATADFQ#(RSDOFIA) is not RNA or DNA")
+
+	_, err := Zuker(seq, temp)
+	require.Error(t, err)
+	assert.Equal(t, expectedErr.Error(), err.Error())
+}

fold/seqfold_test.go

@@ -0,0 +1,43 @@
+package fold
+
+import (
+	"fmt"
+	"math"
+	"testing"
+)
+
+func TestResult_MinimumFreeEnergy_LengthZero(t *testing.T) {
+	result := Result{} // Create a Result instance with empty structs
+
+	expectedEnergy := math.Inf(1)
+	actualEnergy := result.MinimumFreeEnergy()
+
+	if actualEnergy != expectedEnergy {
+		t.Errorf("expected energy to be %f, but got %f", expectedEnergy, actualEnergy)
+	}
+}
+
+func TestResult_DotBracket_LengthZero(t *testing.T) {
+	result := Result{} // Create a Result instance with empty structs
+
+	expectedDotBracket := ""
+	actualDotBracket := result.DotBracket()
+
+	if actualDotBracket != expectedDotBracket {
+		t.Errorf("expected dot bracket to be %s, but got %s", expectedDotBracket, actualDotBracket)
+	}
+}
+
+func TestNewFoldingContext_InvalidSequence(t *testing.T) {
+	seq := "XYZ"
+	temp := 37.0
+
+	_, err := newFoldingContext(seq, temp)
+	if err == nil {
+		t.Errorf("expected error, but got nil")
+	}
+	expectedError := fmt.Errorf("the sequence %s is not RNA or DNA", seq)
+	if err.Error() != expectedError.Error() {
+		t.Errorf("expected error message to be %q, but got %q", expectedError.Error(), err.Error())
+	}
+}