diff --git a/libstdc++-v3/testsuite/25_algorithms/all_of/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/all_of/constexpr.cc
index 11f1a337c20..757eebc89b6 100644
--- a/libstdc++-v3/testsuite/25_algorithms/all_of/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/all_of/constexpr.cc
@@ -23,13 +23,12 @@
 
 constexpr std::array<int, 6> cae{{0, 2, 4, 6, 8, 10}};
 
-constexpr auto out2 = std::all_of(cae.begin(), cae.end(),
+constexpr auto out1 = std::all_of(cae.begin(), cae.end(),
 			          [](int i){ return i % 2 == 0; });
 
-constexpr bool
-test()
-{
-  return true;
-}
+static_assert(out1);
 
-static_assert(test());
+constexpr auto out2 = std::all_of(cae.begin(), cae.end(),
+			          [](int i){ return i != 8; });
+
+static_assert(!out2);
diff --git a/libstdc++-v3/testsuite/25_algorithms/any_of/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/any_of/constexpr.cc
index 370f7f3614a..dadd4506179 100644
--- a/libstdc++-v3/testsuite/25_algorithms/any_of/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/any_of/constexpr.cc
@@ -29,7 +29,10 @@ test()
   const auto out3 = std::any_of(ca0.begin(), ca0.end(),
 			        [](int i){ return i % 2 == 0; });
 
-  return true;
+  const auto out4 = std::any_of(ca0.begin(), ca0.end(),
+			        [](int i){ return i == -1; });
+
+  return out3 && !out4;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/binary_search/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/binary_search/constexpr.cc
index 0e355cc9ba7..f82a6893b48 100644
--- a/libstdc++-v3/testsuite/25_algorithms/binary_search/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/binary_search/constexpr.cc
@@ -31,7 +31,10 @@ test()
   const auto out5 = std::binary_search(ca0.begin(), ca0.end(), 5,
 				       std::less<int>());
 
-  return true;
+  const auto out6 = std::binary_search(ca0.begin(), ca0.end(), 4.5,
+				       std::less<>());
+
+  return out4 && out5 && !out6;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/copy_backward/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/copy_backward/constexpr.cc
index 704dcf513c0..e97e30e0777 100644
--- a/libstdc++-v3/testsuite/25_algorithms/copy_backward/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/copy_backward/constexpr.cc
@@ -30,7 +30,7 @@ test()
   const auto out7 = std::copy_backward(ca0.begin(), ca0.begin() + 8,
 				       ma0.begin() + 10);
 
-  return true;
+  return out7 == ma0.begin() + 2 && ma0[3] == 1;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/count/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/count/constexpr.cc
index 6b6a2801207..3b900a9ca07 100644
--- a/libstdc++-v3/testsuite/25_algorithms/count/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/count/constexpr.cc
@@ -28,7 +28,9 @@ test()
 
   const auto out8 = std::count(ca0.begin(), ca0.end(), 6);
 
-  return true;
+  const auto out9 = std::count(ca0.begin(), ca0.end(), 16);
+
+  return out8 == 1 && out9 == 0;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/equal/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/equal/constexpr.cc
index a3ebee5db90..ca1b7bc5bd9 100644
--- a/libstdc++-v3/testsuite/25_algorithms/equal/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/equal/constexpr.cc
@@ -33,7 +33,12 @@ test()
   const auto outb = std::equal(ca0.begin(), ca0.end(), cas.begin(),
 			       [](int i, int j){ return i + 3 == j; });
 
-  return true;
+  auto ca2 = ca0;
+  ca2[5] = -1;
+
+  const auto outc = std::equal(ca0.begin(), ca0.end(), ca2.begin());
+
+  return outa && outb && !outc;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/equal_range/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/equal_range/constexpr.cc
index 0bd1b0de48c..2b46f5f6759 100644
--- a/libstdc++-v3/testsuite/25_algorithms/equal_range/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/equal_range/constexpr.cc
@@ -28,7 +28,8 @@ test()
 
   const auto outc = std::equal_range(car.begin(), car.end(), 6);
 
-  return true;
+  return outc.first == (car.begin() + 6)
+    && outc.second == (car.begin() + 8);
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/fill/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/fill/constexpr.cc
index ec69a7f432a..154e48b3849 100644
--- a/libstdc++-v3/testsuite/25_algorithms/fill/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/fill/constexpr.cc
@@ -27,7 +27,7 @@ test()
   std::array<int, 12> ma0{{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}};
   std::fill(ma0.begin(), ma0.end(), 66);
 
-  return true;
+  return ma0[4] == 66 && ma0[7] == 66;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/find_end/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/find_end/constexpr.cc
index c5ba3974cfd..9339ab06ae6 100644
--- a/libstdc++-v3/testsuite/25_algorithms/find_end/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/find_end/constexpr.cc
@@ -24,7 +24,7 @@
 constexpr bool
 test()
 {
-  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5,  6, 7, 8,  9, 10, 11}};
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
   constexpr std::array<int, 3> cam{{4, 5, 6}};
   constexpr std::array<int, 3> camm{{-4, -5, -6}};
 
@@ -35,7 +35,7 @@ test()
 				  camm.begin(), camm.end(),
 				  [](int i, int j){ return i + 1 == -j; });
 
-  return true;
+  return outf == (ca0.begin() + 4) && outg == (ca0.begin() + 3);
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/find_if/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/find_if/constexpr.cc
index b4064e6f690..6c88c49c75e 100644
--- a/libstdc++-v3/testsuite/25_algorithms/find_if/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/find_if/constexpr.cc
@@ -24,12 +24,12 @@
 constexpr bool
 test()
 {
-  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5,  6, 7, 8,  9, 10, 11}};
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
 
   const auto outj = std::find_if(ca0.begin(), ca0.end(),
 				 [](int i){ return i == 6; });
 
-  return true;
+  return outj == (ca0.begin() + 6);
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/is_partitioned/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/is_partitioned/constexpr.cc
index deab94d019d..163f9bd2d1d 100644
--- a/libstdc++-v3/testsuite/25_algorithms/is_partitioned/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/is_partitioned/constexpr.cc
@@ -29,7 +29,7 @@ test()
   const auto outs = std::is_partitioned(caeo.begin(), caeo.end(),
 					[](int i){ return i % 2 == 0; });
 
-  return true;
+  return outs;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/is_permutation/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/is_permutation/constexpr.cc
index 1da8bbee30e..1567c2658ff 100644
--- a/libstdc++-v3/testsuite/25_algorithms/is_permutation/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/is_permutation/constexpr.cc
@@ -29,7 +29,9 @@ test()
 
   const auto outt = std::is_permutation(ca0.begin(), ca0.end(), cap.begin());
 
-  return true;
+  const auto outf = std::is_permutation(ca0.begin() + 1, ca0.end(), cap.begin());
+
+  return outt && !outf;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/is_sorted_until/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/is_sorted_until/constexpr.cc
index d000e555ae7..3c540559c31 100644
--- a/libstdc++-v3/testsuite/25_algorithms/is_sorted_until/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/is_sorted_until/constexpr.cc
@@ -31,7 +31,10 @@ test()
   const auto outy = std::is_sorted_until(aus.begin(), aus.end(),
 					 std::less<int>());
 
-  return true;
+  const auto outz = std::is_sorted_until(outx - 1, aus.end(),
+					 std::greater<int>());
+
+  return outx == aus.begin() + 7 && outy == outx && outz == (outx + 1);
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare/constexpr.cc
index 7046f4489d6..1d7502c27c6 100644
--- a/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/lexicographical_compare/constexpr.cc
@@ -34,7 +34,7 @@ test()
 						   ca1.begin(), ca1.end(),
 						   std::less<int>());
 
-  return true;
+  return outz && outaa;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/lower_bound/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/lower_bound/constexpr.cc
index 1b570a2ce54..ec5da9b3227 100644
--- a/libstdc++-v3/testsuite/25_algorithms/lower_bound/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/lower_bound/constexpr.cc
@@ -31,7 +31,7 @@ test()
   const auto outcc = std::lower_bound(ca0.begin(), ca0.end(), 6,
 				      std::less<int>());
 
-  return true;
+  return outbb == (ca0.begin() + 6) && outcc == outbb;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/merge/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/merge/constexpr.cc
index d46b5787b7c..02493581635 100644
--- a/libstdc++-v3/testsuite/25_algorithms/merge/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/merge/constexpr.cc
@@ -31,12 +31,14 @@ test()
 
   const auto outdd = std::merge(ca0.begin(), ca0.end(),
 				cas.begin(), cas.end(), out0.begin());
+  if (outdd != out0.end())
+    return false;
 
   const auto outee = std::merge(ca0.begin(), ca0.end(),
 				camm.begin(), camm.end(), out0.begin(),
 				[](int i, int j){ return i < j; });
 
-  return true;
+  return outee == (out0.begin() + ca0.size() + camm.size());
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/mismatch/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/mismatch/constexpr.cc
index 868bb41e1cb..f2cc21d03d8 100644
--- a/libstdc++-v3/testsuite/25_algorithms/mismatch/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/mismatch/constexpr.cc
@@ -32,7 +32,8 @@ test()
   const auto outgg = std::mismatch(ca0.begin(), ca0.end(), cax.begin(),
 				   std::equal_to<int>());
 
-  return true;
+  return outff.first == (ca0.begin() + 6) && outff.second == (cax.begin() + 6)
+    && outgg == outff;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/none_of/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/none_of/constexpr.cc
index cea4fc61f90..245ebe47dcb 100644
--- a/libstdc++-v3/testsuite/25_algorithms/none_of/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/none_of/constexpr.cc
@@ -29,7 +29,7 @@ test()
   const auto outhh = std::none_of(ca0.begin(), ca0.end(),
 				  [](int i){ return i > 12; });
 
-  return true;
+  return outhh;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/partition_copy/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/partition_copy/constexpr.cc
index e7cb3087b2c..21685636ecd 100644
--- a/libstdc++-v3/testsuite/25_algorithms/partition_copy/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/partition_copy/constexpr.cc
@@ -32,7 +32,8 @@ test()
 					 out0.begin(), out1.begin(),
 					 [](int i){ return i % 2 == 0; });
 
-  return true;
+  return outii.first == (out0.begin() + 6) && out0[1] == 2
+    && outii.second == (out1.begin() + 6) && out1[1] == 3;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/remove_copy/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/remove_copy/constexpr.cc
index 0474feccb09..e82a506abb0 100644
--- a/libstdc++-v3/testsuite/25_algorithms/remove_copy/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/remove_copy/constexpr.cc
@@ -24,12 +24,12 @@
 constexpr bool
 test()
 {
-  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5,  6, 7, 8,  9, 10, 11}};
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
   std::array<int, 24> out0{{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}};
 
   const auto outmm = std::remove_copy(ca0.begin(), ca0.end(), out0.begin(), 6);
 
-  return true;
+  return outmm == out0.begin() + ca0.size() - 1;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/remove_copy_if/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/remove_copy_if/constexpr.cc
index 813be78c133..f8133fc24f5 100644
--- a/libstdc++-v3/testsuite/25_algorithms/remove_copy_if/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/remove_copy_if/constexpr.cc
@@ -30,7 +30,7 @@ test()
   const auto outnn = std::remove_copy_if(ca0.begin(), ca0.end(), out0.begin(),
 					 [](int i){ return i == 7; });
 
-  return true;
+  return outnn == out0.begin() + ca0.size() - 1;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/remove_if/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/remove_if/constexpr.cc
index c2d98f2a68e..d590d4d5ea1 100644
--- a/libstdc++-v3/testsuite/25_algorithms/remove_if/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/remove_if/constexpr.cc
@@ -29,7 +29,7 @@ test()
   const auto outll = std::remove_if(ac2.begin(), ac2.end(),
 				    [](int i){ return i == 7; });
 
-  return true;
+  return outll == (ac2.end() - 1) && ac2[7] == 8;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/replace_if/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/replace_if/constexpr.cc
index 6bcc0bd72ae..4b293f48aa9 100644
--- a/libstdc++-v3/testsuite/25_algorithms/replace_if/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/replace_if/constexpr.cc
@@ -28,7 +28,9 @@ test()
 
   std::replace_if(ar0.begin(), ar0.end(), [](int i){ return i % 2 == 1; }, 42);
 
-  return true;
+  std::array<int, 12> ar1{{0, 42, 2, 42, 4, 42, 6, 6, 8, 42, 42, 42}};
+
+  return ar0 == ar1;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/reverse/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/reverse/constexpr.cc
index ba1f47b6127..15140014a09 100644
--- a/libstdc++-v3/testsuite/25_algorithms/reverse/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/reverse/constexpr.cc
@@ -23,8 +23,6 @@
 constexpr bool
 test()
 {
-  auto ok = true;
-
   std::array<int, 12> ar0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
 
   std::reverse(ar0.begin() + 2, ar0.begin() + 9);
diff --git a/libstdc++-v3/testsuite/25_algorithms/reverse_copy/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/reverse_copy/constexpr.cc
index 86214e1d30e..9a85e591edd 100644
--- a/libstdc++-v3/testsuite/25_algorithms/reverse_copy/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/reverse_copy/constexpr.cc
@@ -29,7 +29,7 @@ test()
 
   const auto outqq = std::reverse_copy(ca0.rbegin(), ca0.rend(), out0.begin());
 
-  return true;
+  return outqq == (out0.begin() + ca0.size()) && out0[3] == 3;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/rotate_copy/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/rotate_copy/constexpr.cc
index f8377b8a24c..8d9d966ba03 100644
--- a/libstdc++-v3/testsuite/25_algorithms/rotate_copy/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/rotate_copy/constexpr.cc
@@ -30,7 +30,7 @@ test()
   const auto outrr = std::rotate_copy(ca0.begin(), ca0.begin() + 6,
 				      ca0.end(), out0.begin());
 
-  return true;
+  return outrr == (out0.begin() + ca0.size()) && out0[3] == 9 && out0[8] == 2;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/search/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/search/constexpr.cc
index e34194cfc5d..557234ec819 100644
--- a/libstdc++-v3/testsuite/25_algorithms/search/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/search/constexpr.cc
@@ -24,7 +24,7 @@
 constexpr bool
 test()
 {
-  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5,  6, 7, 8,  9, 10, 11}};
+  constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
   constexpr std::array<int, 3> cam{{4, 5, 6}};
 
   const auto outtt = std::search(ca0.begin(), ca0.end(),
@@ -35,7 +35,7 @@ test()
     = std::search(ca0.begin(), ca0.end(),
 		  std::default_searcher(cam.begin(), cam.end()));
 
-  return true;
+  return outtt == (ca0.begin() + 4) && outtt2 == outtt;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/set_difference/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/set_difference/constexpr.cc
index ef0f7184604..f66c957df80 100644
--- a/libstdc++-v3/testsuite/25_algorithms/set_difference/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/set_difference/constexpr.cc
@@ -29,13 +29,16 @@ test()
   std::array<int, 24> out0{{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}};
 
   const auto outvv = std::set_difference(ca0.begin(), ca0.end(),
-					 cas.begin(), cas.end(), out0.begin());
+					 cas.begin(), cas.end(),
+					 out0.begin());
 
   const auto outww = std::set_difference(ca0.begin(), ca0.end(),
 				         cas.begin(), cas.end(),
-				         out0.begin(), std::less<int>());
+				         outvv,
+					 std::less<int>());
 
-  return true;
+
+  return outvv == (out0.begin() + 3) && outww == (outvv + 3);
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/set_intersection/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/set_intersection/constexpr.cc
index b415020943a..720e8a5a6c0 100644
--- a/libstdc++-v3/testsuite/25_algorithms/set_intersection/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/set_intersection/constexpr.cc
@@ -36,7 +36,7 @@ test()
 					   cas.begin(), cas.end(),
 					   out0.begin(), std::less<int>());
 
-  return true;
+  return outxx == (out0.begin() + 9) && outyy == outxx;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/set_symmetric_difference/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/set_symmetric_difference/constexpr.cc
index ef0f7184604..0505aaf2519 100644
--- a/libstdc++-v3/testsuite/25_algorithms/set_symmetric_difference/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/set_symmetric_difference/constexpr.cc
@@ -25,17 +25,19 @@ constexpr bool
 test()
 {
   constexpr std::array<int, 12> ca0{{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}};
-  constexpr std::array<int, 12> cas{{3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14}};
+  constexpr std::array<int, 12> cas{{4, 4, 5, 6, 7, 8, 9, 10, 11, 11, 12, 13}};
   std::array<int, 24> out0{{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}};
 
-  const auto outvv = std::set_difference(ca0.begin(), ca0.end(),
-					 cas.begin(), cas.end(), out0.begin());
+  const auto outvv = std::set_symmetric_difference(ca0.begin(), ca0.end(),
+						   cas.begin(), cas.end(),
+						   out0.begin());
 
-  const auto outww = std::set_difference(ca0.begin(), ca0.end(),
-				         cas.begin(), cas.end(),
-				         out0.begin(), std::less<int>());
+  const auto outww = std::set_symmetric_difference(ca0.begin(), ca0.end(),
+						   cas.begin(), cas.end(),
+						   out0.begin(),
+						   std::less<int>());
 
-  return true;
+  return outvv == (out0.begin() + 8) && outww == outvv;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/set_union/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/set_union/constexpr.cc
index fccfe2099d7..87f3f27f9e1 100644
--- a/libstdc++-v3/testsuite/25_algorithms/set_union/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/set_union/constexpr.cc
@@ -29,13 +29,14 @@ test()
   std::array<int, 24> out0{{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}};
 
   const auto out11 = std::set_union(ca0.begin(), ca0.end(),
-				    cas.begin(), cas.end(), out0.begin());
+				    cas.begin(), cas.end(),
+				    out0.begin());
 
   const auto out22 = std::set_union(ca0.begin(), ca0.end(),
 				    cas.begin(), cas.end(),
 				    out0.begin(), std::less<int>());
 
-  return true;
+  return out11 == (out0.begin() + 15) && out22 == out11;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/unique_copy/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/unique_copy/constexpr.cc
index 167dc55add6..ee372b8488d 100644
--- a/libstdc++-v3/testsuite/25_algorithms/unique_copy/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/unique_copy/constexpr.cc
@@ -29,10 +29,11 @@ test()
 
   const auto out55 = std::unique_copy(ar3.begin(), ar3.end(), out0.begin());
 
-  const auto out66 = std::unique_copy(ar3.begin(), ar3.end(), out0.begin(),
+  const auto out66 = std::unique_copy(ar3.begin(), ar3.end(), out55,
 				      std::equal_to<int>());
 
-  return true;
+  return out55 == (out0.begin() + 10) && out0[7] == 8
+    && out66 == (out55 + 10) ; // && out0[19] == 11;
 }
 
 static_assert(test());
diff --git a/libstdc++-v3/testsuite/25_algorithms/upper_bound/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/upper_bound/constexpr.cc
index 8dedb6bd615..3479116c210 100644
--- a/libstdc++-v3/testsuite/25_algorithms/upper_bound/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/upper_bound/constexpr.cc
@@ -31,7 +31,7 @@ test()
   const auto out88 = std::upper_bound(ca0.begin(), ca0.end(), 6,
 				      std::less<int>());
 
-  return true;
+  return out77 == (ca0.begin() + 7) && out88 == out77;
 }
 
 static_assert(test());