  The goal of group testing is to efficiently identify a few specific items,
called positives, in a large population of items via tests. A test is an action
on a subset of items which returns positive if the subset contains at least one
positive and negative otherwise. In non-adaptive group testing, all tests are
fixed in advance and can be performed in parallel. In this work, we consider
non-adaptive group testing with consecutive positives in which the items are
linearly ordered and the positives are consecutive in that order.
  We present two contributions here. The first is the direct use of a binary
code to construct measurement matrices compared to the use of Gray code in the
state-of-the-art work, which is a rearrangement of the binary code, when the
maximum number of consecutive positives is known. This leads to a reduction in
decoding time in practice. The second one is efficient designs to identify
positives when the number of consecutive positives is known. To the best of our
knowledge, this setting has not been surveyed yet. Our simulations verify the
efficiency of our proposed designs. In particular, it only requires up to $300$
tests to identify up to $100$ positives in a set of $2^{32} \approx
4.3\mathrm{B}$ items in less than $300$ nanoseconds. When the maximum number of
consecutive positives is known, the simulations validate the superiority of our
proposed design in decoding compared to the state-of-the-art work. Moreover,
when the number of consecutive positives is known, the number of tests and the
decoding time are almost reduced half.
