Add failing sparse matrix equals tests

Author: Feynman Liang

mllib/src/test/scala/org/apache/spark/mllib/linalg/MatricesSuite.scala

@@ -74,6 +74,22 @@ class MatricesSuite extends SparkFunSuite {
     }
   }
 
+  test("equals") {
+    val dm1 = Matrices.dense(2, 2, Array(0.0, 1.0, 2.0, 3.0))
+    assert(dm1 === dm1)
+    assert(dm1 !== dm1.transpose)
+
+    val dm2 = Matrices.dense(2, 2, Array(0.0, 2.0, 1.0, 3.0))
+    assert(dm1 === dm2.transpose)
+
+    val sm1 = dm1.toSparse
+    assert(sm1 === sm1)
+    assert(sm1 !== sm1.transpose)
+
+    val sm2 = dm2.toSparse
+    assert(sm1 === sm2.transpose)
+  }
+
   test("matrix copies are deep copies") {
     val m = 3
     val n = 2