diff --git a/fixtures/errors/fixture-unexpandable-2.yaml b/fixtures/errors/fixture-unexpandable-2.yaml
index f1358c7..e59f206 100644
--- a/fixtures/errors/fixture-unexpandable-2.yaml
+++ b/fixtures/errors/fixture-unexpandable-2.yaml
@@ -32,6 +32,22 @@ paths:
           description: OK
           schema:
             $ref: '#/thisIs/anAbitrary/jsonPointer/toNowhere'
+  /wrong:
+    get:
+      operationId: target type mismatch
+      responses:
+        '200':
+          description: OK
+          schema:
+            $ref: '#/parameters/someWhere'
+  /wrongcode:
+    get:
+      operationId: target type mismatch
+      responses:
+        'two-hundred':
+          description: OK
+          schema:
+            type: string
 definitions:
   somePlace:
     type: string
diff --git a/flatten_test.go b/flatten_test.go
index 3cad8d6..4d34933 100644
--- a/flatten_test.go
+++ b/flatten_test.go
@@ -863,13 +863,13 @@ func TestOperationIDs(t *testing.T) {
 	an := New(sp)
 	require.NoError(t, Flatten(FlattenOpts{Spec: an, BasePath: bp, Verbose: false, Minimal: false, RemoveUnused: false}))
 
-	res := operations.GatherOperations(New(sp), []string{"getSomeWhere", "getSomeWhereElse"})
-	_, ok := res["getSomeWhere"]
-	assert.Truef(t, ok, "Expected to find operation")
-	_, ok = res["getSomeWhereElse"]
-	assert.Truef(t, ok, "Expected to find operation")
-	_, ok = res["postSomeWhere"]
-	assert.Falsef(t, ok, "Did not expect to find operation")
+	t.Run("should GatherOperations", func(t *testing.T) {
+		res := operations.GatherOperations(New(sp), []string{"getSomeWhere", "getSomeWhereElse"})
+
+		assert.Containsf(t, res, "getSomeWhere", "expected to find operation")
+		assert.Containsf(t, res, "getSomeWhereElse", "expected to find operation")
+		assert.NotContainsf(t, res, "postSomeWhere", "did not expect to find operation")
+	})
 
 	op, ok := an.OperationFor("GET", "/some/where/else")
 	assert.True(t, ok)
diff --git a/internal/antest/helpers.go b/internal/antest/helpers.go
index 42341d7..bcefe63 100644
--- a/internal/antest/helpers.go
+++ b/internal/antest/helpers.go
@@ -45,11 +45,11 @@ func initPathLoader() {
 	}
 }
 
-// LoadSpec loads a json a yaml spec
+// LoadSpec loads a json or a yaml spec
 func LoadSpec(path string) (*spec.Swagger, error) {
 	oncePathLoader.Do(initPathLoader)
 
-	data, err := swag.YAMLDoc(path)
+	data, err := spec.PathLoader(path)
 	if err != nil {
 		return nil, err
 	}
diff --git a/internal/antest/helpers_test.go b/internal/antest/helpers_test.go
new file mode 100644
index 0000000..97fae6b
--- /dev/null
+++ b/internal/antest/helpers_test.go
@@ -0,0 +1,104 @@
+package antest
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestLongTestEnabled(t *testing.T) {
+	t.Run("should be false by default", func(t *testing.T) {
+		require.False(t, LongTestsEnabled())
+	})
+}
+
+func TestLoadSpecErrorCases(t *testing.T) {
+	t.Run("should not load invalid path", func(t *testing.T) {
+		_, err := LoadSpec("nowhere.json")
+		require.Error(t, err)
+	})
+
+	t.Run("should not load invalid YAML", func(t *testing.T) {
+		invalidYAMLFile, clean := prepareBadDoc(t, "yaml", true)
+		t.Cleanup(clean)
+
+		_, err := LoadSpec(invalidYAMLFile)
+		require.Error(t, err)
+	})
+
+	t.Run("should not load invalid JSON", func(t *testing.T) {
+		invalidJSONFile, clean := prepareBadDoc(t, "json", true)
+		t.Cleanup(clean)
+
+		_, err := LoadSpec(invalidJSONFile)
+		require.Error(t, err)
+	})
+
+	t.Run("should not load invalid spec", func(t *testing.T) {
+		invalidJSONFile, clean := prepareBadDoc(t, "json", false)
+		t.Cleanup(clean)
+
+		_, err := LoadSpec(invalidJSONFile)
+		require.Error(t, err)
+	})
+}
+
+func prepareBadDoc(t testing.TB, kind string, invalidFormat bool) (string, func()) {
+	t.Helper()
+
+	var (
+		file string
+		data []byte
+	)
+
+	switch kind {
+	case "yaml", "yml":
+		f, err := os.CreateTemp("", "*.yaml")
+		require.NoError(t, err)
+		file = f.Name()
+
+		if invalidFormat {
+			data = []byte(`--
+zig:
+  zag 3, 4
+`)
+		} else {
+			data = []byte(`--
+swagger: 2
+info:
+  title: true
+`)
+		}
+
+	case "json":
+		f, err := os.CreateTemp("", "*.json")
+		require.NoError(t, err)
+		file = f.Name()
+
+		if invalidFormat {
+			data = []byte(`{
+"zig": {
+  "zag"
+}`)
+		} else {
+			data = []byte(`{
+"swagger": 2
+"info": {
+  "title": true
+}
+}`)
+		}
+
+	default:
+		panic("supports only yaml or json")
+	}
+
+	require.NoError(t,
+		os.WriteFile(file, data, 0600),
+	)
+
+	return file, func() {
+		_ = os.RemoveAll(file)
+	}
+}
diff --git a/internal/flatten/operations/operations_test.go b/internal/flatten/operations/operations_test.go
index 597e454..ac179a9 100644
--- a/internal/flatten/operations/operations_test.go
+++ b/internal/flatten/operations/operations_test.go
@@ -1,5 +1,67 @@
 package operations
 
 import (
+	"testing"
+
 	_ "github.com/go-openapi/analysis/internal/antest"
+	"github.com/go-openapi/spec"
+	"github.com/stretchr/testify/require"
 )
+
+var _ Provider = mockOperationsProvider{}
+
+type mockOperationsProvider struct {
+	give map[string]map[string]*spec.Operation
+}
+
+func (m mockOperationsProvider) Operations() map[string]map[string]*spec.Operation {
+	return m.give
+}
+
+func TestGatherOperations(t *testing.T) {
+	t.Run("should handle empty operation IDs", func(_ *testing.T) {
+		m := mockOperationsProvider{
+			give: map[string]map[string]*spec.Operation{
+				"get": {
+					"/pth1": {
+						OperationProps: spec.OperationProps{
+							ID:          "",
+							Description: "ok",
+						},
+					},
+				},
+			},
+		}
+
+		res := GatherOperations(m, nil)
+		require.Contains(t, res, "GetPth1")
+	})
+
+	t.Run("should handle duplicate operation IDs (when spec validation is skipped)", func(_ *testing.T) {
+		m := mockOperationsProvider{
+			give: map[string]map[string]*spec.Operation{
+				"get": {
+					"/pth1": {
+						OperationProps: spec.OperationProps{
+							ID:          "id1",
+							Description: "ok",
+						},
+					},
+				},
+				"post": {
+					"/pth2": {
+						OperationProps: spec.OperationProps{
+							ID:          "id1",
+							Description: "ok",
+						},
+					},
+				},
+			},
+		}
+
+		res := GatherOperations(m, nil)
+		require.Contains(t, res, "id1")
+		require.NotContains(t, res, "GetPth1")
+		require.Contains(t, res, "PostPth2")
+	})
+}
diff --git a/internal/flatten/replace/replace_test.go b/internal/flatten/replace/replace_test.go
index 1542429..15ca4e1 100644
--- a/internal/flatten/replace/replace_test.go
+++ b/internal/flatten/replace/replace_test.go
@@ -93,33 +93,64 @@ func TestRewriteSchemaRef(t *testing.T) {
 	}
 }
 
-//nolint:dogsled
 func TestReplace_ErrorHandling(t *testing.T) {
 	t.Parallel()
 
-	const wantedFailure = "Expected a failure"
+	const wantedFailure = "expected a failure"
 	bp := filepath.Join("..", "..", "..", "fixtures", "errors", "fixture-unexpandable-2.yaml")
-
-	// reload original spec
 	sp := antest.LoadOrFail(t, bp)
 
-	require.Errorf(t, RewriteSchemaToRef(sp, "#/invalidPointer/key", spec.Ref{}), wantedFailure)
-
-	require.Errorf(t, rewriteParentRef(sp, "#/invalidPointer/key", spec.Ref{}), wantedFailure)
-
-	require.Errorf(t, UpdateRef(sp, "#/invalidPointer/key", spec.Ref{}), wantedFailure)
-
-	require.Errorf(t, UpdateRefWithSchema(sp, "#/invalidPointer/key", &spec.Schema{}), wantedFailure)
-
-	_, _, err := getPointerFromKey(sp, "#/invalidPointer/key")
-	require.Errorf(t, err, wantedFailure)
-
-	_, _, err = getPointerFromKey(sp, "--->#/invalidJsonPointer")
-	require.Errorf(t, err, wantedFailure)
-
-	_, _, _, err = getParentFromKey(sp, "#/invalidPointer/key")
-	require.Errorf(t, err, wantedFailure)
-
-	_, _, _, err = getParentFromKey(sp, "--->#/invalidJsonPointer")
-	require.Errorf(t, err, wantedFailure)
+	t.Run("with invalid $ref", func(t *testing.T) {
+		const ref = "#/invalidPointer/key"
+
+		require.Errorf(t, RewriteSchemaToRef(sp, ref, spec.Ref{}), wantedFailure)
+		require.Errorf(t, rewriteParentRef(sp, ref, spec.Ref{}), wantedFailure)
+		require.Errorf(t, UpdateRef(sp, ref, spec.Ref{}), wantedFailure)
+		require.Errorf(t, UpdateRefWithSchema(sp, ref, &spec.Schema{}), wantedFailure)
+		_, _, err := getPointerFromKey(sp, ref)
+		require.Errorf(t, err, wantedFailure)
+
+		_, _, _, err = getParentFromKey(sp, ref)
+		require.Errorf(t, err, wantedFailure)
+	})
+
+	t.Run("with invalid jsonpointer formatting", func(t *testing.T) {
+		const pointer = "-->#/invalidJsonPointer"
+
+		_, _, err := getPointerFromKey(sp, pointer)
+		require.Errorf(t, err, wantedFailure)
+
+		_, _, _, err = getParentFromKey(sp, pointer)
+		require.Errorf(t, err, wantedFailure)
+	})
+
+	t.Run("with invalid target", func(t *testing.T) {
+		require.Errorf(t, RewriteSchemaToRef(sp, "#/parameters/someWhere", spec.Ref{}), wantedFailure)
+	})
+
+	t.Run("with invalid response target", func(t *testing.T) {
+		const ref = "#/paths/~1wrong/get/responses/200"
+		require.Errorf(t, RewriteSchemaToRef(sp, ref, spec.Ref{}), wantedFailure)
+	})
+
+	t.Run("with invalid response code", func(t *testing.T) {
+		const ref = "#/paths/~1wrongcode/get/responses/two-hundred"
+		require.Errorf(t, rewriteParentRef(sp, ref, spec.Ref{}), wantedFailure)
+	})
+
+	t.Run("with panic case", func(t *testing.T) {
+		t.Run("should not call with types other than *Schema or *Swagger", func(t *testing.T) {
+			require.Panics(t, func() {
+				getPointerFromKey("oops", "#/key")
+			})
+
+			require.Panics(t, func() {
+				getParentFromKey("oops", "#/key")
+			})
+
+			require.Panics(t, func() {
+				UpdateRef("oops", "#/key", spec.Ref{})
+			})
+		})
+	})
 }