0MSG: matches any configuration with no in-flight messages
1MSG: matches any configuration with a single in-flight message
2MSG: matches any configuration with 2 in-flight messages
3MSG: matches any configuration with 3 in-flight messages
4MSG: matches any configuration with 4 in-flight messages
5MSG: matches any configuration with 5 in-flight messages
6MSG: matches any configuration with 6 in-flight messages
7MSG: matches any configuration with 7 in-flight messages
8MSG: matches any configuration with 8 in-flight messages
9MSG: matches any configuration with 9 in-flight messages
IMMEDIATE_REPLACEMENT: matches a configuration with a message replaced by an immediate message
INIT: matches the initial configuration
ORDERED_REPLACEMENT: matches a configuration with a message replaced by an ordered message
UNORDERED_REPLACEMENT: matches a configuration with a message replaced by an unordered message
VALID: matches any valid configuration (is typically negated)