Added missing unit tests for book 1 chapter 10.

tests/test_b1_ch10.py

+import unittest
+
+from src.parser import Parser
+from src.node import ExpressionNode as N, ExpressionLeaf as L
+from tests.parser import run_expressions
+
+
+class TestB1Ch10(unittest.TestCase):
+
+    def test_diagnostic_test(self):
+        run_expressions(Parser, [
+            ('5(a-2b)', N('*', L(5), N('-', L('a'),
+                                       N('*', L(2), L('b'))))),
+            ('-(3a+6b)', N('-', N('+', N('*', L(3), L('a')),
+                                  N('*', L(6), L('b'))))),
+            ('18-(a-12)', N('-', L(18),
+                            N('-', L('a'), L(12)))),
+            ('-p-q+5(p-q)-3q-2(p-q)',
+                N('-',
+                  N('-',
+                    N('+', N('-', N('-', L('p')), L('q')),
+                      N('*', L(5), N('-', L('p'), L('q')))),
+                    N('*', L(3), L('q'))
+                  ),
+                  N('*', L(2), N('-', L('p'), L('q')))
+                )
+            ),
+            ('(2+3/7)^4',
+                N('^', N('+', L(2), N('/', L(3), L(7))), L(4))
+            ),
+            ('x3*x2*x',
+                N('*',
+                  N('*',
+                    N('^', L('x'), L(3)),
+                    N('^', L('x'), L(2))),
+                  L('x')
+                )
+            ),
+            ('-x3*-2x5',
+                N('*',
+                  N('*',
+                    N('-', N('^', L('x'), L(3))),
+                    N('-', L(2))),
+                  N('^', L('x'), L(5))
+                )
+            ),
+            ('(7x2y3)^2/(7x2y3)',
+                N('*',
+                  N('*',
+                    N('-', N('^', L('x'), L(3))),
+                    N('-', L(2))),
+                  N('^', L('x'), L(5))
+                )
+            ),
+            ])