add unittest for new mean/median/quantile# masking conditions

tests/test_probabilist.cpp

@@ -193,7 +193,7 @@ TEST(ProbabilistTests, TestMaskingConditions)
     // generate dummy empty masks required to access next optional argument
     xt::xtensor<bool, 4> masks;
 
-    // conditions on streamflow ________________________________________________
+    // conditions on streamflow values _________________________________________
 
     // compute scores using masking conditions on streamflow to subset whole record
     xt::xtensor<std::array<char, 32>, 2> q_conditions = {
@@ -226,6 +226,42 @@ TEST(ProbabilistTests, TestMaskingConditions)
         ) << "Failure for (" << metrics[m] << ")";
     }
 
+    // conditions on streamflow statistics _____________________________________
+
+    // compute scores using masking conditions on streamflow to subset whole record
+    xt::xtensor<std::array<char, 32>, 2> q_conditions_ = {
+            {{"q_prd_mean{>=median}"}}
+    };
+
+    auto q_prd_mean = xt::mean(predicted, {0}, xt::keep_dims);
+    double median = xt::median(q_prd_mean);
+
+    std::vector<xt::xarray<double>> metrics_q_conditioned_ =
+            evalhyd::evalp(
+                    observed,
+                    xt::view(predicted, xt::newaxis(), xt::newaxis(), xt::all(), xt::all()),
+                    metrics, thresholds,
+                    masks, q_conditions_
+            );
+
+    // compute scores using "NaN-ed" time indices where conditions on streamflow met
+    std::vector<xt::xarray<double>> metrics_q_preconditioned_ =
+            evalhyd::evalp(
+                    xt::where(q_prd_mean >= median, observed, NAN),
+                    xt::view(predicted, xt::newaxis(), xt::newaxis(), xt::all(), xt::all()),
+                    metrics, thresholds
+            );
+
+    // check results are identical
+    for (int m = 0; m < metrics.size(); m++)
+    {
+        EXPECT_TRUE(
+                xt::allclose(
+                        metrics_q_conditioned_[m], metrics_q_preconditioned_[m]
+                )
+        ) << "Failure for (" << metrics[m] << ")";
+    }
+
     // conditions on temporal indices __________________________________________
 
     // compute scores using masking conditions on time indices to subset whole record