tests: fix `is_successful()` deprecation

tests/dates.py

@@ -6,7 +6,7 @@ from .utils import execute, KOSMORRO
 def test_with_date():
     for arg in [["-d", "2020-01-27"], ["--date", "2020-01-27"], ["-d2020-01-27"]]:
         result = execute(KOSMORRO + arg)
-        assert result.is_successful()
+        assert result.successful
 
         assert (
             result.stdout
@@ -27,7 +27,7 @@ def test_with_incorrect_date_values():
     value = "yolo-yo-lo"
     for arg in [["-d", value], ["--date", value], [f"-d{value}"]]:
         result = execute(KOSMORRO + arg)
-        assert not result.is_successful()
+        assert not result.successful
         assert (
             result.stderr
             == f"The date {value} does not match the required YYYY-MM-DD format or the offset format.\n"
@@ -36,7 +36,7 @@ def test_with_incorrect_date_values():
     value = "2020-13-32"
     for arg in [["-d", value], ["--date", value], [f"-d{value}"]]:
         result = execute(KOSMORRO + arg)
-        assert not result.is_successful()
+        assert not result.successful
         assert (
             result.stderr == f"The date {value} is not valid: month must be in 1..12\n"
         )
@@ -45,7 +45,7 @@ def test_with_incorrect_date_values():
 def test_with_out_of_range_dates():
     for arg in [["-d", "1789-05-05"], ["-d", "3000-01-01"]]:
         result = execute(KOSMORRO + arg)
-        assert not result.is_successful()
+        assert not result.successful
         assert (
             result.stderr
             == "Moon phase can only be computed between August 9, 1899 and September 26, 2053\nThe date must be between July 28, 1899 and October 8, 2053\n"
@@ -55,7 +55,7 @@ def test_with_out_of_range_dates():
 def test_with_out_of_range_dates_for_moon_phase_only():
     for arg in [["-d", "1899-07-30"], ["-d", "2053-10-06"]]:
         result = execute(KOSMORRO + arg)
-        assert result.is_successful()
+        assert result.successful
         assert (
             result.stderr
             == "Moon phase can only be computed between August 9, 1899 and September 26, 2053\n"

tests/general.py

@@ -13,7 +13,7 @@ from babel.dates import format_date
 
 def test_run_without_argument():
     result = execute(KOSMORRO)
-    assert result.is_successful()
+    assert result.successful
 
     stdout = result.stdout.split("\n")
     print(stdout)
@@ -34,7 +34,7 @@ def test_help_message():
     for arg in ["--help", "-h"]:
         result = execute(KOSMORRO + [arg])
 
-        assert result.is_successful()
+        assert result.successful
 
         if python_version.major == 3 and python_version.minor < 13:
             assert (

tests/output.py

@@ -13,7 +13,7 @@ def test_json_output():
     result = execute(
         KOSMORRO + ["--position=50.5876,3.0624", "-d2020-01-27", "--format=json"]
     )
-    assert result.is_successful()
+    assert result.successful
     assert (
         result.stdout
         == """{

tests/position.py

@@ -7,7 +7,7 @@ from .utils import (
 
 
 def check_command_return(result):
-    assert result.is_successful()
+    assert result.successful
     assert (
         result.stdout
         == """Monday, January 27, 2020

tests/timezone.py

@@ -7,7 +7,7 @@ from .utils import (
 
 
 def check_command_return_t_plus_one(result):
-    assert result.is_successful()
+    assert result.successful
     assert (
         result.stdout
         == """Monday, January 27, 2020
@@ -24,7 +24,7 @@ Note: All the hours are given in the UTC+1 timezone.
 
 
 def check_command_return_t_minus_one(result):
-    assert result.is_successful()
+    assert result.successful
     assert (
         result.stdout
         == """Monday, January 27, 2020