Add option to read lists of tests from file.

```
-i FILE, --tests-file=FILE
    Loads the list of tests to execute from a file. Each line in the
    file is interpreted as the name of a test, or a group of tests, to
    execute, just like the tests would be specified on the command
    line. Empty lines and lines starting with ``#`` are ignored. (This
    format is compatible with that of the ``btest`` `StateFile
    <state_file_>`_.)
```

README

@@ -400,6 +400,14 @@ and 1 otherwise. Exit code 1 can also result in case of other errors.
     Retry any failed tests up to this many times to determine if
     they are unstable.
 
+-i FILE, --tests-file=FILE
+    Loads the list of tests to execute from a file. Each line in the
+    file is interpreted as the name of a test, or a group of tests, to
+    execute, just like the tests would be specified on the command
+    line. Empty lines and lines starting with ``#`` are ignored. (This
+    format is compatible with that of the ``btest`` `StateFile
+    <state_file_>`_.)
+
 .. _configuration file: configuration_
 .. _configuration:
 
@@ -558,6 +566,8 @@ configuration file:
     range.  The default range is "1024-65535".
 
 ``StateFile``
+    .. _state_file:
+
     The name of the state file to record the names of failing tests. Default is
     ``.btest.failed.dat``.
 

btest

@@ -193,12 +193,12 @@ def getOption(key, default, section="btest"):
 reBackticks = re.compile(r"`(([^`]|`)*)`")
 
 
-def readStateFile():
+def readTestsFile(file):
     try:
         # Read state file.
         tests = []
 
-        for line in open(StateFile):
+        for line in open(file, encoding="utf-8"):
             line = line.strip()
             if not line or line.startswith("#"):
                 continue
@@ -2937,6 +2937,15 @@ def parse_options():
             "Can be specified multiple times."
         ),
     )
+    optparser.add_option(
+        "-i",
+        "--tests-file",
+        action="store",
+        type="string",
+        dest="tests_file",
+        default="",
+        help=("Load list of tests to execute from file."),
+    )
 
     optparser.set_defaults(mode="TEST")
 
@@ -3201,11 +3210,17 @@ if __name__ == "__main__":
         Config.configured_tests = findTests(testdirs, True)
 
     if args:
+        if Options.tests_file:
+            error("cannot specify tests both on command line and with --tests-file")
+
         tests = findTests(args)
 
     else:
         if Options.rerun:
-            (success, tests) = readStateFile()
+            if Options.tests_file:
+                error("cannot specify both --rerun and --tests-file")
+
+            (success, tests) = readTestsFile(StateFile)
 
             if success:
                 if not tests:
@@ -3216,6 +3231,12 @@ if __name__ == "__main__":
                 warning("cannot read state file, executing all tests")
                 tests = Config.configured_tests
 
+        elif Options.tests_file:
+            (success, tests) = readTestsFile(Options.tests_file)
+
+            if not success:
+                warning("cannot read file with tests: %s" % Options.tests_file)
+
         else:
             tests = Config.configured_tests
 

testing/Baseline/tests.tests-file/output

@@ -0,0 +1,8 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+t1 ... ok
+t2 ... failed
+t3 ... ok
+1 of 3 tests failed
+t1 ... ok
+t3 ... ok
+all 2 tests successful

testing/tests/tests-file.test

@@ -0,0 +1,20 @@
+# %TEST-EXEC-FAIL: btest t1 t2 t3 >>output 2>&1
+# %TEST-EXEC: btest -i my-tests >>output 2>&1
+# %TEST-EXEC: btest-diff output
+
+%TEST-START-FILE t1
+@TEST-EXEC: exit 0
+%TEST-END-FILE
+
+%TEST-START-FILE t2
+@TEST-EXEC: exit 1
+%TEST-END-FILE
+
+%TEST-START-FILE t3
+@TEST-EXEC: exit 0
+%TEST-END-FILE
+
+%TEST-START-FILE my-tests
+t1
+t3
+%TEST-END-FILE