1 files changed, 70 insertions, 0 deletions
diff --git a/spec/lib/gitlab/utils/inline_hash_spec.rb b/spec/lib/gitlab/utils/inline_hash_spec.rb
new file mode 100644
index 00000000000..867db0b92a5
--- /dev/null
+++ b/spec/lib/gitlab/utils/inline_hash_spec.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+describe Gitlab::Utils::InlineHash do
+  describe '.merge_keys' do
+    subject { described_class.merge_keys(source) }
+
+    let(:source) do
+      {
+        nested_param: {
+          key: :Value
+        },
+        'root_param' => 'Root',
+        unnested_symbol_key: :unnested_symbol_value,
+        12 => 22,
+        'very' => {
+          'deep' => {
+            'nested' => {
+              'param' => 'Deep nested value'
+            }
+          }
+        }
+      }
+    end
+
+    it 'transforms a nested hash into a one-level hash' do
+      is_expected.to eq(
+        'nested_param.key' => :Value,
+        'root_param' => 'Root',
+        :unnested_symbol_key => :unnested_symbol_value,
+        12 => 22,
+        'very.deep.nested.param' => 'Deep nested value'
+      )
+    end
+
+    it 'retains key insertion order' do
+      expect(subject.keys)
+        .to eq(['nested_param.key', 'root_param', :unnested_symbol_key, 12, 'very.deep.nested.param'])
+    end
+
+    context 'with a custom connector' do
+      subject { described_class.merge_keys(source, connector: '::') }
+
+      it 'uses the connector to merge keys' do
+        is_expected.to eq(
+          'nested_param::key' => :Value,
+          'root_param' => 'Root',
+          :unnested_symbol_key => :unnested_symbol_value,
+          12 => 22,
+          'very::deep::nested::param' => 'Deep nested value'
+        )
+      end
+    end
+
+    context 'with a starter prefix' do
+      subject { described_class.merge_keys(source, prefix: 'options') }
+
+      it 'prefixes all the keys' do
+        is_expected.to eq(
+          'options.nested_param.key' => :Value,
+          'options.root_param' => 'Root',
+          'options.unnested_symbol_key' => :unnested_symbol_value,
+          'options.12' => 22,
+          'options.very.deep.nested.param' => 'Deep nested value'
+        )
+      end
+    end
+  end
+end