fix unit test

Signed-off-by: ananzh <ananzh@amazon.com>

src/plugins/discover/public/application/view_components/utils/filter_columns.test.ts

@@ -12,23 +12,22 @@ describe('filterColumns', () => {
       getAll: () => [{ name: 'a' }, { name: 'c' }, { name: 'd' }],
     },
   } as IndexPattern;
-  const defaultColumns = ['_defaultColumn'];
 
   it('should return columns that exist in the index pattern fields', () => {
     const columns = ['a', 'b'];
-    const result = filterColumns(columns, indexPatternMock, defaultColumns);
+    const result = filterColumns(columns, indexPatternMock, ['a']);
     expect(result).toEqual(['a']);
   });
 
   it('should return defaultColumns if no columns exist in the index pattern fields', () => {
     const columns = ['b', 'e'];
-    const result = filterColumns(columns, indexPatternMock, defaultColumns);
-    expect(result).toEqual(defaultColumns);
+    const result = filterColumns(columns, indexPatternMock, ['e']);
+    expect(result).toEqual(['_source']);
   });
 
-  it('should return defaultColumns if no columns and indexPattern is null', () => {
+  it('should return defaultColumns if no columns and indexPattern is undefined', () => {
     const columns = ['b', 'e'];
-    const result = filterColumns(columns, null, defaultColumns);
-    expect(result).toEqual(defaultColumns);
+    const result = filterColumns(columns, undefined, ['a']);
+    expect(result).toEqual(['_source']);
   });
 });