deprecate and refactor: deprecate camelCase functions in diffpy.srfit.equation and refactor test for pytest format

news/equation-tests.rst

@@ -0,0 +1,41 @@
+**Added:**
+
+* Add ``make_equation``, ``register_constant``, ``register_argument``,
+  ``register_operator``, ``register_builder`` and ``deregister_builder`` to
+  ``EquationFactory``, and ``wrap_argument``, ``wrap_operator``,
+  ``wrap_function`` and ``get_builder`` to ``diffpy.srfit.equation.builder``.
+* Add ``Equation.set_root``, ``Operator.add_literal`` and ``make_operator`` to
+  ``diffpy.srfit.equation``.
+* Add ``get_args``, ``get_expression`` and ``pretty_print`` to
+  ``diffpy.srfit.equation.visitors``, and ``on_argument``, ``on_operator`` and
+  ``on_equation`` to ``Visitor``.
+
+**Changed:**
+
+* ``OperatorABC`` now requires ``add_literal`` instead of ``addLiteral``, and
+  ``Visitor`` subclasses now override ``on_argument``, ``on_operator`` and
+  ``on_equation`` instead of ``onArgument``, ``onOperator`` and
+  ``onEquation``.
+
+**Deprecated:**
+
+* ``EquationFactory.makeEquation``, ``registerConstant``, ``registerArgument``,
+  ``registerOperator``, ``registerBuilder`` and ``deRegisterBuilder``,
+  ``wrapArgument``, ``wrapOperator``, ``wrapFunction``, ``getBuilder``,
+  ``Equation.setRoot``, ``Operator.addLiteral``, ``makeOperator``,
+  ``getArgs``, ``getExpression``, ``prettyPrint`` and ``Visitor.onArgument``,
+  ``onOperator`` and ``onEquation`` are deprecated in favor of their
+  snake_case replacements. The old names still work and warn, and will be
+  removed in version 4.0.0.
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* Fix the test check for observers left on global equation builders.
+
+**Security:**
+
+* <news item>