Selects substring matching. The match succeeds if the output contains
the content string. This is the default value for checks without
a matcher option, or where the value of matcher is
CONTENT_MATCHER_OPTION_UNSPECIFIED.
MatchesRegex
Selects regular-expression matching. The match succeeds of the output
matches the regular expression specified in the content string.
NotContainsString
Selects negation of substring matching. The match succeeds if the
output does NOT contain the content string.
NotMatchesRegex
Selects negation of regular-expression matching. The match succeeds if
the output does NOT match the regular expression specified in the
content string.
Unspecified
No content matcher type specified (maintained for backward
compatibility, but deprecated for future use).
Treated as CONTAINS_STRING.
