Using Jira cloud
Following Advanced search reference - JQL fields cloud documentation.
This clause:
and issueLinkType = "is tested by"
returns 3 results, as expected.
This clause:
and issueLinkType != "is tested by"
returns 0 results, whereas about 8 are expected.
Try to extends your JQL query in the way:
(issueLinkType != "is tested by" OR issueLinkType is EMPTY)
I ran into this problem myself wondering why and where the rest disappears, "is EMPTY" comes to the rescue for some of fields.
Roman
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