Update test functions to use expect_line assertion

Refactor tests to use expect_line for output checks.

Author: razorblade23

foundations/02_add_numbers/test_add_numbers.py

@@ -1,21 +1,18 @@
 import pytest
 
 
-def test_prints_the_sum(run_script):
+def test_prints_the_sum(run_script, expect_line):
     stdout, _ = run_script("add_numbers.py")
-    lines = stdout.strip().splitlines()
-    assert lines[0] == "11"
+    expect_line(stdout, 1, "11")
 
 
 @pytest.mark.skip(reason="unlock once the test above passes")
-def test_prints_the_difference(run_script):
+def test_prints_the_difference(run_script, expect_line):
     stdout, _ = run_script("add_numbers.py")
-    lines = stdout.strip().splitlines()
-    assert lines[1] == "5"
+    expect_line(stdout, 2, "5")
 
 
 @pytest.mark.skip(reason="unlock once the test above passes")
-def test_prints_the_product(run_script):
+def test_prints_the_product(run_script, expect_line):
     stdout, _ = run_script("add_numbers.py")
-    lines = stdout.strip().splitlines()
-    assert lines[2] == "24"
+    expect_line(stdout, 3, "24")