Validate triangular dist parameters on startup

src/ert/config/gen_kw_config.py

@@ -205,6 +205,25 @@ def _check_non_negative_parameter(param: str, prior: PriorDict) -> None:
                     ).set_context(self.name)
                 )
 
+        def _check_valid_triangular_parameters(prior: PriorDict) -> None:
+            key = prior["key"]
+            dist = prior["function"]
+            xmin, xmode, xmax = prior["parameters"].values()
+            if not (xmin < xmax):
+                errors.append(
+                    ErrorInfo(
+                        f"Minimum {xmin} must be strictly less than the maxiumum {xmax}"
+                        f" for {dist} distributed parameter {key}",
+                    ).set_context(self.name)
+                )
+            if not (xmin <= xmode <= xmax):
+                errors.append(
+                    ErrorInfo(
+                        f"The mode {xmode} must be between the minimum {xmin} and maximum {xmax}"
+                        f" for {dist} distributed parameter {key}",
+                    ).set_context(self.name)
+                )
+
         unique_keys = set()
         for prior in self.get_priors():
             key = prior["key"]
@@ -219,6 +238,8 @@ def _check_non_negative_parameter(param: str, prior: PriorDict) -> None:
             if prior["function"] == "LOGNORMAL":
                 _check_non_negative_parameter("MEAN", prior)
                 _check_non_negative_parameter("STD", prior)
+            elif prior["function"] == "TRIANGULAR":
+                _check_valid_triangular_parameters(prior)
             elif prior["function"] in {"NORMAL", "TRUNCATED_NORMAL"}:
                 _check_non_negative_parameter("STD", prior)
         if errors:

tests/ert/unit_tests/config/test_gen_kw_config.py

@@ -625,3 +625,59 @@ def test_suggestion_on_empty_parameter_file(tmp_path):
                 ],
             }
         )
+
+
+@pytest.mark.parametrize(
+    "distribution, min, mode, max, error",
+    [
+        ("TRIANGULAR", "0", "2", "3", None),
+        (
+            "TRIANGULAR",
+            "3.0",
+            "3.0",
+            "3.0",
+            "Minimum 3.0 must be strictly less than the maxiumum 3.0",
+        ),
+        ("TRIANGULAR", "-1", "0", "1", None),
+        (
+            "TRIANGULAR",
+            "3.0",
+            "6.0",
+            "5.5",
+            "The mode 6.0 must be between the minimum 3.0 and maximum 5.5",
+        ),
+        (
+            "TRIANGULAR",
+            "3.0",
+            "-6.0",
+            "5.5",
+            "The mode -6.0 must be between the minimum 3.0 and maximum 5.5",
+        ),
+    ],
+)
+def test_validation_triangular_distribution(
+    tmpdir, distribution, min, mode, max, error
+):
+    with tmpdir.as_cwd():
+        config = dedent(
+            """
+        JOBNAME my_name%d
+        NUM_REALIZATIONS 1
+        GEN_KW KW_NAME template.txt kw.txt prior.txt
+        """
+        )
+        with open("config.ert", "w", encoding="utf-8") as fh:
+            fh.writelines(config)
+        with open("template.txt", "w", encoding="utf-8") as fh:
+            fh.writelines("MY_KEYWORD <MY_KEYWORD>")
+        with open("prior.txt", "w", encoding="utf-8") as fh:
+            fh.writelines(f"MY_KEYWORD {distribution} {min} {mode} {max}")
+
+        if error:
+            with pytest.raises(
+                ConfigValidationError,
+                match=error,
+            ):
+                ErtConfig.from_file("config.ert")
+        else:
+            ErtConfig.from_file("config.ert")