Harden read-only provider with tests, docs, and CI

internal/provider/mappers_test.go

@@ -0,0 +1,44 @@
+package provider
+
+import (
+	"testing"
+
+	"github.com/dynu/terraform-provider-dynu/internal/dynuclient"
+)
+
+func TestSortDomains(t *testing.T) {
+	domains := []dynuclient.Domain{
+		{ID: 2, Name: "z.example.com"},
+		{ID: 1, Name: "a.example.com"},
+		{ID: 3, Name: "a.example.com"},
+	}
+
+	sortDomains(domains)
+
+	if domains[0].ID != 1 || domains[1].ID != 3 || domains[2].ID != 2 {
+		t.Fatalf("unexpected domain sort order: %#v", domains)
+	}
+}
+
+func TestSortDNSRecords(t *testing.T) {
+	records := []dynuclient.DNSRecord{
+		{ID: 3, Hostname: "b.example.com", RecordType: "TXT"},
+		{ID: 1, Hostname: "a.example.com", RecordType: "A"},
+		{ID: 2, Hostname: "a.example.com", RecordType: "A"},
+	}
+
+	sortDNSRecords(records)
+
+	if records[0].ID != 1 || records[1].ID != 2 || records[2].ID != 3 {
+		t.Fatalf("unexpected record sort order: %#v", records)
+	}
+}
+
+func TestMapString(t *testing.T) {
+	if !mapString("").IsNull() {
+		t.Fatal("expected empty string to map to null")
+	}
+	if mapString("value").ValueString() != "value" {
+		t.Fatal("expected non-empty string to map to value")
+	}
+}