[schema][algorithm] add test for param choice len

Any "choice" type parameter needs >=3 choices to be valid
(otherwise it could be a boolean or a constant)

beat/core/test/prefix/algorithms/schema/invalid_choice_parameter/6.json

+{
+    "api_version": 2,
+    "schema_version": 3,
+    "splittable": false,
+    "type": "sequential",
+    "uses": {},
+    "description": "this is an example of an algorithm with an invalid choice parameter (choice count needs to be >=3)",
+    "groups": [
+        {
+            "name": "group",
+            "inputs": {
+                "input": {
+                    "type": "user/single_integer/1"
+                }
+            },
+            "outputs": {
+                "output": {
+                    "type": "user/single_integer/1"
+                }
+            }
+        }
+    ],
+    "language": "python",
+    "parameters": {
+        "testparam": {
+            "choice": [
+                0,
+                1
+            ],
+            "type": "float32"
+        }
+    }
+}

beat/core/test/prefix/algorithms/schema/invalid_choice_parameter/6.py

+#!/usr/bin/env python
+# vim: set fileencoding=utf-8 :
+
+###################################################################################
+#                                                                                 #
+# Copyright (c) 2019 Idiap Research Institute, http://www.idiap.ch/               #
+# Contact: beat.support@idiap.ch                                                  #
+#                                                                                 #
+# Redistribution and use in source and binary forms, with or without              #
+# modification, are permitted provided that the following conditions are met:     #
+#                                                                                 #
+# 1. Redistributions of source code must retain the above copyright notice, this  #
+# list of conditions and the following disclaimer.                                #
+#                                                                                 #
+# 2. Redistributions in binary form must reproduce the above copyright notice,    #
+# this list of conditions and the following disclaimer in the documentation       #
+# and/or other materials provided with the distribution.                          #
+#                                                                                 #
+# 3. Neither the name of the copyright holder nor the names of its contributors   #
+# may be used to endorse or promote products derived from this software without   #
+# specific prior written permission.                                              #
+#                                                                                 #
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND #
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED   #
+# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE          #
+# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE    #
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL      #
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR      #
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER      #
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,   #
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE   #
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.            #
+#                                                                                 #
+###################################################################################
+
+
+class Algorithm:
+    def process(self, inputs, outputs):
+        return True

beat/core/test/test_algorithm_loading.py

@@ -193,6 +193,10 @@ def test_invalid_choice_parameters():
     algorithm = Algorithm(prefix, "schema/invalid_choice_parameter/5")
     nose.tools.assert_false(algorithm.valid)
 
+    # needs >=3 choices
+    algorithm = Algorithm(prefix, "schema/invalid_choice_parameter/6")
+    nose.tools.assert_false(algorithm.valid)
+
 
 # ----------------------------------------------------------