Add preliminary tests

src/Sparse/Row.jl

@@ -105,6 +105,14 @@ function Base.empty!(A::SRow)
   return A
 end
 
+function Base.empty(A::SRow)
+  return sparse_row(base_ring(A))
+end
+
+function zero(A::SRow)
+  return empty(A)
+end
+
 function swap!(A::SRow, B::SRow)
   A.pos, B.pos = B.pos, A.pos
   A.values, B.values = B.values, A.values

test/Sparse/Row.jl

@@ -204,4 +204,33 @@
   B = sparse_row(F,[1],[y])
   C = add_scaled_row(A,B,F(1))
   @test C == A+B
+
+  # mutating arithmetic
+  randcoeff() = rand(-20:20)
+  Main.equality(A::SRow, B::SRow) = A == B
+  for _ in 1:10
+    maxind_A = rand(0:10)
+    inds_A = Hecke.Random.randsubseq(1:maxind_A, rand())
+    vals_A = [rand(ZZ, -10:10) for _ in 1:length(inds_A)]
+    A = sparse_row(FlintZZ, inds_A, vals_A)
+
+    maxind_B = rand(0:10)
+    inds_B = Hecke.Random.randsubseq(1:maxind_B, rand())
+    vals_B = [rand(ZZ, -10:10) for _ in 1:length(inds_B)]
+    B = sparse_row(FlintZZ, inds_B, vals_B)
+
+    test_mutating_op_like_zero(zero, zero!, A)
+
+    test_mutating_op_like_neg(-, neg!, A)
+
+    test_mutating_op_like_add(+, add!, A, B)
+    test_mutating_op_like_add(-, sub!, A, B)
+    # test_mutating_op_like_add(*, mul!, A, randcoeff())
+    # test_mutating_op_like_add(*, mul!, randcoeff(), A)
+    # test_mutating_op_like_add(*, mul!, A, ZZ(randcoeff()))
+    # test_mutating_op_like_add(*, mul!, ZZ(randcoeff()), A)
+
+    # test_mutating_op_like_addmul((a, b, c) -> a + b*c, addmul!, A, B, randcoeff())
+    # test_mutating_op_like_addmul((a, b, c) -> a - b*c, submul!, A, B, randcoeff())
+  end
 end