Implemented the remaining trim artifact cleanup

internal/trim/artifact_test.go

@@ -128,6 +128,61 @@ func TestConvertArtifactMinimalToFullFails(t *testing.T) {
 	}
 }
 
+func TestValidateArtifactRejectsMissingPayloads(t *testing.T) {
+	tests := []struct {
+		name     string
+		artifact Artifact
+		want     string
+	}{
+		{
+			name:     "full",
+			artifact: Artifact{Schema: SchemaFull},
+			want:     "full artifact payload is missing",
+		},
+		{
+			name:     "intermediate",
+			artifact: Artifact{Schema: SchemaIntermediate},
+			want:     "intermediate artifact payload is missing",
+		},
+		{
+			name:     "minimal",
+			artifact: Artifact{Schema: SchemaMinimal},
+			want:     "minimal artifact payload is missing",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			err := ValidateArtifact(test.artifact)
+			assertErrorContains(t, err, test.want)
+		})
+	}
+}
+
+func TestApplyArtifactRejectsMissingPayload(t *testing.T) {
+	_, err := ApplyArtifact(Artifact{Schema: SchemaFull}, Options{})
+	assertErrorContains(t, err, "full artifact payload is missing")
+}
+
+func TestConvertArtifactRejectsMissingPayloadWhenConversionRequested(t *testing.T) {
+	_, err := ConvertArtifact(Artifact{Schema: SchemaFull}, SchemaMinimal)
+	assertErrorContains(t, err, "full artifact payload is missing")
+}
+
+func TestConvertArtifactSameSchemaDoesNotRequirePayload(t *testing.T) {
+	artifact := Artifact{Schema: SchemaFull}
+	converted, err := ConvertArtifact(artifact, SchemaFull)
+	if err != nil {
+		t.Fatalf("convert failed: %v", err)
+	}
+	if converted.Schema != SchemaFull {
+		t.Fatalf("schema = %q, want %q", converted.Schema, SchemaFull)
+	}
+	if converted.Full != nil {
+		t.Fatalf("full payload = %#v, want nil", converted.Full)
+	}
+}
+
 func mustMarshalJSON(t *testing.T, value any) []byte {
 	t.Helper()
 	data, err := json.Marshal(value)