1 files changed, 126 insertions, 0 deletions
diff --git a/internal/resource/repository_test.go b/internal/resource/repository_test.go
new file mode 100644
index 0000000..8f1aef6
--- /dev/null
+++ b/internal/resource/repository_test.go
@@ -0,0 +1,126 @@
+package resource
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+// mockApplier records the order in which Apply was called.
+type mockApplier struct {
+	name string
+	err  error
+	logs *[]string
+}
+
+func (m *mockApplier) Apply() error {
+	*m.logs = append(*m.logs, m.name)
+	return m.err
+}
+
+func TestApply(t *testing.T) {
+	tests := []struct {
+		name        string
+		setup       func(r *repository, logs *[]string)
+		wantOrder   []string
+		wantError   bool
+		errorString string
+	}{
+		{
+			name: "dependency chain",
+			setup: func(r *repository, logs *[]string) {
+				// A depends on B, B depends on C
+				r.registered["A"] = Resource{
+					Type: "T", Name: "A",
+					Apply: &mockApplier{name: "A", logs: logs},
+					dependsOn: map[string]struct{}{"B": {}},
+				}
+				r.registered["B"] = Resource{
+					Type: "T", Name: "B",
+					Apply: &mockApplier{name: "B", logs: logs},
+					dependsOn: map[string]struct{}{"C": {}},
+				}
+				r.registered["C"] = Resource{
+					Type: "T", Name: "C",
+					Apply: &mockApplier{name: "C", logs: logs},
+				}
+			},
+			wantOrder: []string{"C", "B", "A"},
+		},
+		{
+			name: "circular dependency",
+			setup: func(r *repository, logs *[]string) {
+				r.registered["A"] = Resource{
+					Type: "T", Name: "A",
+					Apply: &mockApplier{name: "A", logs: logs},
+					dependsOn: map[string]struct{}{"B": {}},
+				}
+				r.registered["B"] = Resource{
+					Type: "T", Name: "B",
+					Apply: &mockApplier{name: "B", logs: logs},
+					dependsOn: map[string]struct{}{"A": {}},
+				}
+			},
+			wantError:   true,
+			errorString: "circular dependency",
+		},
+		{
+			name: "missing dependency",
+			setup: func(r *repository, logs *[]string) {
+				r.registered["A"] = Resource{
+					Type: "T", Name: "A",
+					Apply: &mockApplier{name: "A", logs: logs},
+					dependsOn: map[string]struct{}{"Missing": {}},
+				}
+			},
+			wantError:   true,
+			errorString: "not registered",
+		},
+		{
+			name: "execution failure",
+			setup: func(r *repository, logs *[]string) {
+				r.registered["A"] = Resource{
+					Type: "T", Name: "A",
+					Apply: &mockApplier{name: "A", err: errors.New("fail A"), logs: logs},
+				}
+			},
+			wantError:   true,
+			errorString: "failed to apply",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ResetRepository()
+			logs := make([]string, 0)
+			r := getRepository()
+			tt.setup(r, &logs)
+
+			err := Apply()
+
+			if (err != nil) != tt.wantError {
+				t.Errorf("Apply() error = %v, wantError %v", err, tt.wantError)
+				return
+			}
+
+			if tt.wantError && tt.errorString != "" {
+				if err == nil || !strings.Contains(err.Error(), tt.errorString) {
+					t.Errorf("Apply() error = %v, want error containing %q", err, tt.errorString)
+				}
+			}
+
+			if !tt.wantError && tt.wantOrder != nil {
+				if len(logs) != len(tt.wantOrder) {
+					t.Errorf("Apply() log length = %d, want %d", len(logs), len(tt.wantOrder))
+					return
+				}
+				for i := range logs {
+					if logs[i] != tt.wantOrder[i] {
+						t.Errorf("Apply() order = %v, want %v", logs, tt.wantOrder)
+						break
+					}
+				}
+			}
+		})
+	}
+}