diff --git a/pdbtools/pdb_add_manual_ter.py b/pdbtools/pdb_add_manual_ter.py
new file mode 100644
index 00000000..26a29b6c
--- /dev/null
+++ b/pdbtools/pdb_add_manual_ter.py
@@ -0,0 +1,288 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+#
+# Copyright 2021 Brian Andrews
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Adds TER entries at locations in pdb designated by the user. Starting residue
+must be specified to avoid inconsistent behavior. This program is agnostic to
+residue numbers in the pdb file. The first residue of the pdb file will be
+considered residue one (1) and TER entries will be entered at specified intervals
+using that convention. Existing TER entries will not be affected.
+
+Usage:
+    python pdb_addter.py -[first residue]:[last residue]:[frequency] <pdb file>
+
+Example:
+    python pdb_addter.py -1:10 1CTF.pdb # Adds TER after every residue starting with the end of residue 1 to before residue 10
+    python pdb_addter.py -1::3 1CTF.pdb # Adds TER after every 3th residue starting from residue 1
+    python pdb_addter.py -1:10:5 1CTF.pdb # Adds TER after every 5th residue from residues 1 to 10
+    python pdb_addter.py -4: 1CTF.pdb # Adds TER after every residue starting at the end of residue 4
+
+This program is part of the `pdb-tools` suite of utilities and should not be
+distributed isolatedly. The `pdb-tools` were created to quickly manipulate PDB
+files using the terminal, and can be used sequentially, with one tool streaming
+data to another. They are based on old FORTRAN77 code that was taking too much
+effort to maintain and compile. RIP.
+"""
+
+import os
+import sys
+
+__author__ = ["Joao Rodrigues", "Brian Andrews"]
+__email__ = ["j.p.g.l.m.rodrigues@gmail.com", "b9andrews@gmail.com"]
+
+
+def check_input(args):
+    """Checks whether to read from stdin/file and validates user input/options.
+    """
+
+    def return_integer(string):
+        try:
+            return int(string)
+        except:
+            emsg = 'ERROR!! Range values must be integers!\n'
+            sys.stderr.write(emsg.format(string))
+            sys.exit(1)
+
+    # Defaults
+    option = ':::'
+    fh = sys.stdin  # file handle
+
+    if not len(args):
+        # Reading from pipe with default option
+        if sys.stdin.isatty():
+            sys.stderr.write(__doc__)
+            sys.exit(1)
+
+    elif len(args) == 1:
+        # One of two options: option & Pipe OR file & default option
+        if args[0].startswith('-'):
+            option = args[0][1:]
+            if sys.stdin.isatty():  # ensure the PDB data is streamed in
+                emsg = 'ERROR!! No data to process!\n'
+                sys.stderr.write(emsg)
+                sys.stderr.write(__doc__)
+                sys.exit(1)
+
+        else:
+            if not os.path.isfile(args[0]):
+                emsg = 'ERROR!! File not found or not readable: \'{}\'\n'
+                sys.stderr.write(emsg.format(args[0]))
+                sys.stderr.write(__doc__)
+                sys.exit(1)
+
+            fh = open(args[0], 'r')
+
+    elif len(args) == 2:
+        # Two options: option & File
+        if not args[0].startswith('-'):
+            emsg = 'ERROR! First argument is not an option: \'{}\'\n'
+            sys.stderr.write(emsg.format(args[0]))
+            sys.stderr.write(__doc__)
+            sys.exit(1)
+
+        if not os.path.isfile(args[1]):
+            emsg = 'ERROR!! File not found or not readable: \'{}\'\n'
+            sys.stderr.write(emsg.format(args[1]))
+            sys.stderr.write(__doc__)
+            sys.exit(1)
+
+        option = args[0][1:]
+        fh = open(args[1], 'r')
+
+    else:  # Whatever ...
+        sys.stderr.write(__doc__)
+        sys.exit(1)
+
+    # Validate option
+    if not (1 <= option.count(':') <= 2):
+        emsg = 'ERROR!! Residue range must be in \'a:z:s\' where a and z are '
+        emsg += 'optional (default to first residue and last respectively), and '
+        emsg += 's is an optional step value (to return every s-th residue).\n'
+        sys.stderr.write(emsg)
+        sys.exit(1)
+
+    start, end, step = None, None, 1
+    slices = [num if num.strip() else None for num in option.split(':')]
+    if len(slices) == 3:
+        start, end, step = slices
+    elif len(slices) == 2:
+        start, end = slices
+    elif len(slices) == 1:
+        if option.startswith(':'):
+            end = slices[0]
+        elif option.endswith(':'):
+            start = slices[0]
+
+    #residue range start
+    if start is None:
+        emsg = 'ERROR!! Please specify starting value: \'{}\'\n'
+        sys.stderr.write(emsg.format(start))
+        sys.exit(1)
+    else:
+        start = return_integer(start)
+
+    if  start < 1:
+        emsg = 'ERROR!! Starting value must be 1 or greater: \'{}\'\n'
+        sys.stderr.write(emsg.format(start))
+        sys.exit(1)
+
+    #residue range end
+    if end is None:
+        end = 1000000  # a value that presumably will not be reached
+    else:
+        end = return_integer(end)
+
+    if start >= end:
+        emsg = 'ERROR!! Start ({}) cannot be larger than end ({})\n'
+        sys.stderr.write(emsg.format(start, end))
+        sys.exit(1)
+
+    #residue range step
+    if step is None:
+        step = 1
+    else:
+        step = return_integer(step)
+
+    if step <= 0:
+        emsg = 'ERROR!! Step value must be a positive number: \'{}\'\n'
+        sys.stderr.write(emsg.format(step))
+        sys.exit(1)
+
+    resrange = set(range(start, end + 2)) #plus 2 here is necessary
+    return (fh, resrange, step)
+
+
+def run(fhandle, residue_range, step):
+    """
+    Add TER records within the residue range at frequency identified by step.
+
+    This function is a generator.
+
+    Parameters
+    ----------
+    fhandle : a line-by-line iterator of the original PDB file.
+
+    residue_range : set, list, or tuple
+        The residues describing the range to consider.
+
+    step : int
+        The step at which to insert a TER record.
+
+    Yields
+    ------
+    str (line-by-line)
+        All lines with added TER lines designated by inputs.
+    """
+
+    def make_TER(prev_line):
+        """Creates a TER statement based on the last ATOM/HETATM line.
+        """
+
+        # Add last TER statement
+        serial = int(prev_line[6:11]) + 1
+        rname = prev_line[17:20]
+        chain = prev_line[21]
+        resid = prev_line[22:26]
+        icode = prev_line[26]
+
+        return fmt_TER.format(serial, rname, chain, resid, icode)
+
+    # TER     606      LEU A  75
+    fmt_TER = "TER   {:>5d}      {:3s} {:1s}{:>4s}{:1s}" + " " * 53 + "\n"
+
+    prev_line = None
+    prev_res = None
+    res_counter = 0
+    no_more_atoms = False
+    atom_counter = 0
+    min_residue = min(residue_range)
+    records = ('ATOM', 'HETATM', 'ANISOU')
+    ignored = ('TER')
+    end = ('END', 'ENDMDL', 'CONECT')
+    for line in fhandle:
+        if line.startswith(records):
+
+            res_id = line[21:26]  # include chain ID
+            if res_id != prev_res:
+
+                prev_res = res_id
+                res_counter += 1
+                if res_counter - min_residue != 0 \
+                  and (res_counter - min_residue) % step == 0 \
+                  and res_counter in residue_range \
+                  and not prev_line.startswith(ignored): #does not add TER record if one exists
+                    atom_counter += 1
+                    yield make_TER(prev_line)
+
+            #adjusts atom numbers for added TER entries
+            atom_counter += 1
+            line = line[:6] + str(atom_counter).rjust(5) + line[11:]
+
+        #modifies atom number of existing TER entries - also changes 'TER\n' to full 'TER' entries
+        if line.startswith(ignored):
+            atom_counter += 1
+            yield make_TER(prev_line)
+
+        # sees record that indicates end of ATOMS records, checks if TER record should be
+        # added based on user input only once.
+        if line.startswith(end) \
+          and res_counter in residue_range \
+          and res_counter % step == 0 \
+          and not prev_line.startswith(ignored) \
+          and not no_more_atoms:
+            no_more_atoms = True
+            atom_counter += 1
+            yield make_TER(prev_line)
+
+        prev_line = line
+        if not line.startswith(ignored):
+            yield line
+
+add_manual_ter = run
+
+def main():
+    # Check Input
+    pdbfh, resrange, step = check_input(sys.argv[1:])
+
+    # Do the job
+    new_pdb = run(pdbfh, resrange, step)
+
+    try:
+        _buffer = []
+        _buffer_size = 5000  # write N lines at a time
+        for lineno, line in enumerate(new_pdb):
+            if not (lineno % _buffer_size):
+                sys.stdout.write(''.join(_buffer))
+                _buffer = []
+            _buffer.append(line)
+
+        sys.stdout.write(''.join(_buffer))
+        sys.stdout.flush()
+    except IOError:
+        # This is here to catch Broken Pipes
+        # for example to use 'head' or 'tail' without
+        # the error message showing up
+        pass
+
+    # last line of the script
+    # We can close it even if it is sys.stdin
+    pdbfh.close()
+    sys.exit(0)
+
+
+if __name__ == '__main__':
+    main()
diff --git a/tests/data/add_manual_ter_existingTER.pdb b/tests/data/add_manual_ter_existingTER.pdb
new file mode 100644
index 00000000..61562108
--- /dev/null
+++ b/tests/data/add_manual_ter_existingTER.pdb
@@ -0,0 +1,75 @@
+CRYST1    0.000    0.000    0.000  90.00  90.00  90.00 P 1           1
+ATOM      1  N   ALA X   1      -0.132   2.450  -0.112  0.80  0.00      1    N
+ATOM      2  C   ALA X   1       0.301   0.419  -1.423  0.80  0.00      1    C
+ATOM      3  O   ALA X   1       0.479  -0.783  -1.242  0.80  0.00      1    O
+ATOM      4  CA  ALA X   1      -0.701   1.208  -0.598  0.80  0.00      1    C
+ATOM      5  CB  ALA X   1      -1.903   1.542  -1.431  0.80  0.00      1    C
+ATOM      6  HA  ALA X   1      -0.992   0.670   0.193  0.80  0.00      1    H
+ATOM      7  HT1 ALA X   1       0.220   3.108  -0.747  0.80  0.00      1    H
+ATOM      8  HT2 ALA X   1      -0.767   3.067   0.352  0.80  0.00      1    H
+ATOM      9  HB1 ALA X   1      -2.108   2.634  -1.418  0.80  0.00      1    H
+ATOM     10  HB2 ALA X   1      -1.743   1.237  -2.489  0.80  0.00      1    H
+ATOM     11  HB3 ALA X   1      -2.803   1.018  -1.044  0.80  0.00      1    H
+TER
+ATOM     12  N   ALA X   2       0.969   1.064  -2.333  0.80  0.00      1    N
+ATOM     13  C   ALA X   2       3.021  -0.294  -2.323  0.80  0.00      1    C
+ATOM     14  O   ALA X   2       3.374  -1.452  -2.536  0.80  0.00      1    O
+ATOM     15  CA  ALA X   2       1.956   0.379  -3.172  0.80  0.00      1    C
+ATOM     16  HA  ALA X   2       1.468  -0.304  -3.715  0.80  0.00      1    H
+ATOM     17  CB  ALA X   2       2.588   1.376  -4.097  0.80  0.00      1    C
+ATOM     18  HN  ALA X   2       0.833   2.036  -2.485  0.80  0.00      1    H
+ATOM     19  HB1 ALA X   2       3.693   1.256  -4.120  0.80  0.00      1    H
+ATOM     20  HB2 ALA X   2       2.208   1.245  -5.134  0.80  0.00      1    H
+ATOM     21  HB3 ALA X   2       2.362   2.413  -3.766  0.80  0.00      1    H
+ATOM     22  N   ALA X   3       3.552   0.402  -1.362  0.80  0.00      1    N
+ATOM     23  C   ALA X   3       4.097  -1.439   0.176  0.80  0.00      1    C
+ATOM     24  O   ALA X   3       4.783  -2.459   0.205  0.80  0.00      1    O
+ATOM     25  CA  ALA X   3       4.589  -0.170  -0.499  0.80  0.00      1    C
+ATOM     26  HA  ALA X   3       5.382  -0.373  -1.074  0.80  0.00      1    H
+ATOM     27  CB  ALA X   3       4.982   0.845   0.533  0.80  0.00      1    C
+ATOM     28  HN  ALA X   3       3.271   1.339  -1.184  0.80  0.00      1    H
+ATOM     29  HB1 ALA X   3       5.946   0.573   1.014  0.80  0.00      1    H
+ATOM     30  HB2 ALA X   3       5.101   1.849   0.070  0.80  0.00      1    H
+ATOM     31  HB3 ALA X   3       4.208   0.912   1.328  0.80  0.00      1    H
+ATOM     32  N   ALA X   4       2.921  -1.408   0.730  0.80  0.00      1    N
+ATOM     33  C   ALA X   4       2.321  -3.779   0.466  0.80  0.00      1    C
+ATOM     34  O   ALA X   4       2.725  -4.888   0.812  0.80  0.00      1    O
+ATOM     35  CA  ALA X   4       2.374  -2.587   1.406  0.80  0.00      1    C
+ATOM     36  HA  ALA X   4       2.967  -2.790   2.185  0.80  0.00      1    H
+ATOM     37  CB  ALA X   4       0.998  -2.267   1.911  0.80  0.00      1    C
+ATOM     38  HN  ALA X   4       2.360  -0.588   0.710  0.80  0.00      1    H
+ATOM     39  HB1 ALA X   4       0.950  -1.232   2.313  0.80  0.00      1    H
+ATOM     40  HB2 ALA X   4       0.250  -2.351   1.092  0.80  0.00      1    H
+ATOM     41  HB3 ALA X   4       0.709  -2.966   2.726  0.80  0.00      1    H
+ATOM     42  N   ALA X   5       1.827  -3.587  -0.721  0.80  0.00      1    N
+ATOM     43  C   ALA X   5       3.099  -5.306  -1.938  0.80  0.00      1    C
+ATOM     44  O   ALA X   5       3.260  -6.525  -1.934  0.80  0.00      1    O
+ATOM     45  CA  ALA X   5       1.736  -4.685  -1.687  0.80  0.00      1    C
+ATOM     46  HA  ALA X   5       1.112  -5.368  -1.309  0.80  0.00      1    H
+ATOM     47  CB  ALA X   5       1.164  -4.160  -2.971  0.80  0.00      1    C
+ATOM     48  HN  ALA X   5       1.500  -2.694  -1.008  0.80  0.00      1    H
+ATOM     49  HB1 ALA X   5       1.507  -3.121  -3.167  0.80  0.00      1    H
+ATOM     50  HB2 ALA X   5       1.482  -4.793  -3.829  0.80  0.00      1    H
+ATOM     51  HB3 ALA X   5       0.053  -4.153  -2.930  0.80  0.00      1    H
+ATOM     52  N   ALA X   6       4.095  -4.500  -2.161  0.80  0.00      1    N
+ATOM     53  C   ALA X   6       5.914  -5.897  -1.272  0.80  0.00      1    C
+ATOM     54  O   ALA X   6       6.435  -6.992  -1.476  0.80  0.00      1    O
+ATOM     55  CA  ALA X   6       5.442  -5.017  -2.416  0.80  0.00      1    C
+ATOM     56  HA  ALA X   6       5.406  -5.547  -3.264  0.80  0.00      1    H
+ATOM     57  CB  ALA X   6       6.382  -3.863  -2.602  0.80  0.00      1    C
+ATOM     58  HN  ALA X   6       3.973  -3.514  -2.165  0.80  0.00      1    H
+ATOM     59  HB1 ALA X   6       7.428  -4.158  -2.369  0.80  0.00      1    H
+ATOM     60  HB2 ALA X   6       6.354  -3.500  -3.652  0.80  0.00      1    H
+ATOM     61  HB3 ALA X   6       6.105  -3.022  -1.929  0.80  0.00      1    H
+ATOM     62  N   ALA X   7       5.751  -5.448  -0.063  0.80  0.00      1    N
+ATOM     63  C   ALA X   7       5.524  -7.601   1.108  0.80  0.00      1    C
+ATOM     64  O   ALA X   7       6.173  -8.625   1.312  0.80  0.00      1    O
+ATOM     65  CA  ALA X   7       6.183  -6.232   1.098  0.80  0.00      1    C
+ATOM     66  HA  ALA X   7       7.177  -6.331   1.042  0.80  0.00      1    H
+ATOM     67  CB  ALA X   7       5.836  -5.483   2.351  0.80  0.00      1    C
+ATOM     68  HC1 ALA X   7       4.508  -7.641   0.940  0.80  0.00      1    H
+ATOM     69  HN  ALA X   7       5.331  -4.565   0.111  0.80  0.00      1    H
+ATOM     70  HB1 ALA X   7       6.748  -5.080   2.841  0.80  0.00      1    H
+ATOM     71  HB2 ALA X   7       5.163  -4.628   2.123  0.80  0.00      1    H
+ATOM     72  HB3 ALA X   7       5.324  -6.153   3.076  0.80  0.00      1    H
+END
diff --git a/tests/data/add_manual_ter_test_regular.pdb b/tests/data/add_manual_ter_test_regular.pdb
new file mode 100644
index 00000000..cb46dca2
--- /dev/null
+++ b/tests/data/add_manual_ter_test_regular.pdb
@@ -0,0 +1,74 @@
+CRYST1    0.000    0.000    0.000  90.00  90.00  90.00 P 1           1
+ATOM      1  N   ALA X   1      -0.132   2.450  -0.112  0.80  0.00      1    N
+ATOM      2  C   ALA X   1       0.301   0.419  -1.423  0.80  0.00      1    C
+ATOM      3  O   ALA X   1       0.479  -0.783  -1.242  0.80  0.00      1    O
+ATOM      4  CA  ALA X   1      -0.701   1.208  -0.598  0.80  0.00      1    C
+ATOM      5  CB  ALA X   1      -1.903   1.542  -1.431  0.80  0.00      1    C
+ATOM      6  HA  ALA X   1      -0.992   0.670   0.193  0.80  0.00      1    H
+ATOM      7  HT1 ALA X   1       0.220   3.108  -0.747  0.80  0.00      1    H
+ATOM      8  HT2 ALA X   1      -0.767   3.067   0.352  0.80  0.00      1    H
+ATOM      9  HB1 ALA X   1      -2.108   2.634  -1.418  0.80  0.00      1    H
+ATOM     10  HB2 ALA X   1      -1.743   1.237  -2.489  0.80  0.00      1    H
+ATOM     11  HB3 ALA X   1      -2.803   1.018  -1.044  0.80  0.00      1    H
+ATOM     12  N   ALA X   2       0.969   1.064  -2.333  0.80  0.00      1    N
+ATOM     13  C   ALA X   2       3.021  -0.294  -2.323  0.80  0.00      1    C
+ATOM     14  O   ALA X   2       3.374  -1.452  -2.536  0.80  0.00      1    O
+ATOM     15  CA  ALA X   2       1.956   0.379  -3.172  0.80  0.00      1    C
+ATOM     16  HA  ALA X   2       1.468  -0.304  -3.715  0.80  0.00      1    H
+ATOM     17  CB  ALA X   2       2.588   1.376  -4.097  0.80  0.00      1    C
+ATOM     18  HN  ALA X   2       0.833   2.036  -2.485  0.80  0.00      1    H
+ATOM     19  HB1 ALA X   2       3.693   1.256  -4.120  0.80  0.00      1    H
+ATOM     20  HB2 ALA X   2       2.208   1.245  -5.134  0.80  0.00      1    H
+ATOM     21  HB3 ALA X   2       2.362   2.413  -3.766  0.80  0.00      1    H
+ATOM     22  N   ALA X   3       3.552   0.402  -1.362  0.80  0.00      1    N
+ATOM     23  C   ALA X   3       4.097  -1.439   0.176  0.80  0.00      1    C
+ATOM     24  O   ALA X   3       4.783  -2.459   0.205  0.80  0.00      1    O
+ATOM     25  CA  ALA X   3       4.589  -0.170  -0.499  0.80  0.00      1    C
+ATOM     26  HA  ALA X   3       5.382  -0.373  -1.074  0.80  0.00      1    H
+ATOM     27  CB  ALA X   3       4.982   0.845   0.533  0.80  0.00      1    C
+ATOM     28  HN  ALA X   3       3.271   1.339  -1.184  0.80  0.00      1    H
+ATOM     29  HB1 ALA X   3       5.946   0.573   1.014  0.80  0.00      1    H
+ATOM     30  HB2 ALA X   3       5.101   1.849   0.070  0.80  0.00      1    H
+ATOM     31  HB3 ALA X   3       4.208   0.912   1.328  0.80  0.00      1    H
+ATOM     32  N   ALA X   4       2.921  -1.408   0.730  0.80  0.00      1    N
+ATOM     33  C   ALA X   4       2.321  -3.779   0.466  0.80  0.00      1    C
+ATOM     34  O   ALA X   4       2.725  -4.888   0.812  0.80  0.00      1    O
+ATOM     35  CA  ALA X   4       2.374  -2.587   1.406  0.80  0.00      1    C
+ATOM     36  HA  ALA X   4       2.967  -2.790   2.185  0.80  0.00      1    H
+ATOM     37  CB  ALA X   4       0.998  -2.267   1.911  0.80  0.00      1    C
+ATOM     38  HN  ALA X   4       2.360  -0.588   0.710  0.80  0.00      1    H
+ATOM     39  HB1 ALA X   4       0.950  -1.232   2.313  0.80  0.00      1    H
+ATOM     40  HB2 ALA X   4       0.250  -2.351   1.092  0.80  0.00      1    H
+ATOM     41  HB3 ALA X   4       0.709  -2.966   2.726  0.80  0.00      1    H
+ATOM     42  N   ALA X   5       1.827  -3.587  -0.721  0.80  0.00      1    N
+ATOM     43  C   ALA X   5       3.099  -5.306  -1.938  0.80  0.00      1    C
+ATOM     44  O   ALA X   5       3.260  -6.525  -1.934  0.80  0.00      1    O
+ATOM     45  CA  ALA X   5       1.736  -4.685  -1.687  0.80  0.00      1    C
+ATOM     46  HA  ALA X   5       1.112  -5.368  -1.309  0.80  0.00      1    H
+ATOM     47  CB  ALA X   5       1.164  -4.160  -2.971  0.80  0.00      1    C
+ATOM     48  HN  ALA X   5       1.500  -2.694  -1.008  0.80  0.00      1    H
+ATOM     49  HB1 ALA X   5       1.507  -3.121  -3.167  0.80  0.00      1    H
+ATOM     50  HB2 ALA X   5       1.482  -4.793  -3.829  0.80  0.00      1    H
+ATOM     51  HB3 ALA X   5       0.053  -4.153  -2.930  0.80  0.00      1    H
+ATOM     52  N   ALA X   6       4.095  -4.500  -2.161  0.80  0.00      1    N
+ATOM     53  C   ALA X   6       5.914  -5.897  -1.272  0.80  0.00      1    C
+ATOM     54  O   ALA X   6       6.435  -6.992  -1.476  0.80  0.00      1    O
+ATOM     55  CA  ALA X   6       5.442  -5.017  -2.416  0.80  0.00      1    C
+ATOM     56  HA  ALA X   6       5.406  -5.547  -3.264  0.80  0.00      1    H
+ATOM     57  CB  ALA X   6       6.382  -3.863  -2.602  0.80  0.00      1    C
+ATOM     58  HN  ALA X   6       3.973  -3.514  -2.165  0.80  0.00      1    H
+ATOM     59  HB1 ALA X   6       7.428  -4.158  -2.369  0.80  0.00      1    H
+ATOM     60  HB2 ALA X   6       6.354  -3.500  -3.652  0.80  0.00      1    H
+ATOM     61  HB3 ALA X   6       6.105  -3.022  -1.929  0.80  0.00      1    H
+ATOM     62  N   ALA X   7       5.751  -5.448  -0.063  0.80  0.00      1    N
+ATOM     63  C   ALA X   7       5.524  -7.601   1.108  0.80  0.00      1    C
+ATOM     64  O   ALA X   7       6.173  -8.625   1.312  0.80  0.00      1    O
+ATOM     65  CA  ALA X   7       6.183  -6.232   1.098  0.80  0.00      1    C
+ATOM     66  HA  ALA X   7       7.177  -6.331   1.042  0.80  0.00      1    H
+ATOM     67  CB  ALA X   7       5.836  -5.483   2.351  0.80  0.00      1    C
+ATOM     68  HC1 ALA X   7       4.508  -7.641   0.940  0.80  0.00      1    H
+ATOM     69  HN  ALA X   7       5.331  -4.565   0.111  0.80  0.00      1    H
+ATOM     70  HB1 ALA X   7       6.748  -5.080   2.841  0.80  0.00      1    H
+ATOM     71  HB2 ALA X   7       5.163  -4.628   2.123  0.80  0.00      1    H
+ATOM     72  HB3 ALA X   7       5.324  -6.153   3.076  0.80  0.00      1    H
+END
diff --git a/tests/test_pdb_add_manual_ter.py b/tests/test_pdb_add_manual_ter.py
new file mode 100644
index 00000000..5ef36a83
--- /dev/null
+++ b/tests/test_pdb_add_manual_ter.py
@@ -0,0 +1,385 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+#
+# Copyright 2018 João Pedro Rodrigues
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Unit Tests for `pdb_addter`.
+"""
+
+import os
+import sys
+import unittest
+
+from config import data_dir
+from utils import OutputCapture
+
+
+class TestTool(unittest.TestCase):
+    """
+    Generic class for testing tools.
+    """
+
+    def setUp(self):
+        # Dynamically import the module
+        name = 'pdbtools.pdb_add_manual_ter'
+        self.module = __import__(name, fromlist=[''])
+
+    def exec_module(self):
+        """
+        Execs module.
+        """
+
+        with OutputCapture() as output:
+            try:
+                self.module.main()
+            except SystemExit as e:
+                self.retcode = e.code
+
+        self.stdout = output.stdout
+        self.stderr = output.stderr
+
+        return
+
+    def test_range_1(self):
+        """$ pdb_add_manual_ter -1:5 data/add_manual_ter_test_regular.pdb"""
+
+        # Simulate input
+        sys.argv = ['', '-1:5', os.path.join(data_dir, 'add_manual_ter_test_regular.pdb')]
+
+        # Execute the script
+        self.exec_module()
+
+        # Validate results
+        self.assertEqual(self.retcode, 0)
+        self.assertEqual(len(self.stdout), 79)
+        self.assertEqual(len(self.stderr), 0)
+
+        records = ('TER')
+        ter_locations = [l[0:80] for l in self.stdout if l.startswith(records)]
+
+        expected = ["TER      12      ALA X   1" + " " * 54,
+                    "TER      23      ALA X   2" + " " * 54,
+                    "TER      34      ALA X   3" + " " * 54,
+                    "TER      45      ALA X   4" + " " * 54,
+                    "TER      56      ALA X   5" + " " * 54]
+
+        self.assertEqual(ter_locations, expected)
+
+    def test_range_2(self):
+        """$ pdb_add_manual_ter -1: data/add_manual_ter_test_regular.pdb"""
+
+        # Simulate input
+        sys.argv = ['', '-1:', os.path.join(data_dir, 'add_manual_ter_test_regular.pdb')]
+
+        # Execute the script
+        self.exec_module()
+
+        # Validate results
+        self.assertEqual(self.retcode, 0)
+        self.assertEqual(len(self.stdout), 81)
+        self.assertEqual(len(self.stderr), 0)
+
+        records = ('TER')
+        ter_locations = [l[0:80] for l in self.stdout if l.startswith(records)]
+
+        expected = ["TER      12      ALA X   1" + " " * 54,
+                    "TER      23      ALA X   2" + " " * 54,
+                    "TER      34      ALA X   3" + " " * 54,
+                    "TER      45      ALA X   4" + " " * 54,
+                    "TER      56      ALA X   5" + " " * 54,
+                    "TER      67      ALA X   6" + " " * 54,
+                    "TER      79      ALA X   7" + " " * 54]
+
+        self.assertEqual(ter_locations, expected)
+
+    def test_range_3(self):
+        """$ pdb_add_manual_ter -1:7:3 data/add_manual_ter_test_regular.pdb"""
+
+        # Simulate input
+        sys.argv = ['', '-1:7:3', os.path.join(data_dir, 'add_manual_ter_test_regular.pdb')]
+
+        # Execute the script
+        self.exec_module()
+
+        # Validate results
+        self.assertEqual(self.retcode, 0)
+        self.assertEqual(len(self.stdout), 76)
+        self.assertEqual(len(self.stderr), 0)
+
+        records = ('TER')
+        ter_locations = [l[0:80] for l in self.stdout if l.startswith(records)]
+
+        expected = ["TER      32      ALA X   3" + " " * 54,
+                    "TER      63      ALA X   6" + " " * 54]
+
+        self.assertEqual(ter_locations, expected)
+
+    def test_range_4(self):
+        """$ pdb_add_manual_ter -1::5 data/add_manual_ter_test_regular.pdb"""
+
+        # Simulate input
+        sys.argv = ['', '-1::5', os.path.join(data_dir, 'add_manual_ter_test_regular.pdb')]
+
+        # Execute the script
+        self.exec_module()
+
+        # Validate results
+        self.assertEqual(self.retcode, 0)
+        self.assertEqual(len(self.stdout), 75)
+        self.assertEqual(len(self.stderr), 0)
+
+        records = ('TER')
+        ter_locations = [l[0:80] for l in self.stdout if l.startswith(records)]
+
+        expected = ["TER      52      ALA X   5" + " " * 54]
+
+        self.assertEqual(ter_locations, expected)
+
+    def test_range_5(self):
+        """$ pdb_add_manual_ter -1:: data/add_manual_ter_test_existingTER.pdb"""
+
+        # Simulate input
+        sys.argv = ['', '-1:', os.path.join(data_dir, 'add_manual_ter_existingTER.pdb')]
+
+        # Execute the script
+        self.exec_module()
+
+        # Validate results
+        self.assertEqual(self.retcode, 0)
+        self.assertEqual(len(self.stdout), 81)
+        self.assertEqual(len(self.stderr), 0)
+
+        records = ('TER')
+        ter_locations = [l[0:80] for l in self.stdout if l.startswith(records)]
+
+        expected = ["TER      12      ALA X   1" + " " * 54,
+                    "TER      23      ALA X   2" + " " * 54,
+                    "TER      34      ALA X   3" + " " * 54,
+                    "TER      45      ALA X   4" + " " * 54,
+                    "TER      56      ALA X   5" + " " * 54,
+                    "TER      67      ALA X   6" + " " * 54,
+                    "TER      79      ALA X   7" + " " * 54]
+
+        self.assertEqual(ter_locations, expected)
+
+    def test_range_6(self):
+        """$ pdb_add_manual_ter -1::2 data/add_manual_ter_existingTER.pdb"""
+
+        # Simulate input
+        sys.argv = ['', '-1::2', os.path.join(data_dir, 'add_manual_ter_existingTER.pdb')]
+
+        # Execute the script
+        self.exec_module()
+
+        # Validate results
+        self.assertEqual(self.retcode, 0)
+        self.assertEqual(len(self.stdout), 78)
+        self.assertEqual(len(self.stderr), 0)
+
+        records = ('TER')
+        ter_locations = [l[0:80] for l in self.stdout if l.startswith(records)]
+
+        expected = ["TER      12      ALA X   1" + " " * 54,
+                    "TER      23      ALA X   2" + " " * 54,
+                    "TER      44      ALA X   4" + " " * 54,
+                    "TER      65      ALA X   6" + " " * 54]
+
+        self.assertEqual(ter_locations, expected)
+
+    def test_range_7(self):
+        """$ pdb_add_manual_ter -1: data/dummy.pdb"""
+
+        # Simulate input
+        sys.argv = ['', '-1:', os.path.join(data_dir, 'dummy.pdb')]
+
+        # Execute the script
+        self.exec_module()
+
+        # Validate results
+        self.assertEqual(self.retcode, 0)
+        self.assertEqual(len(self.stdout), 220)
+        self.assertEqual(len(self.stderr), 0)
+
+        records = ('TER')
+        ter_locations = [l[0:80] for l in self.stdout if l.startswith(records)]
+
+        #issue where TER automatically increments line number needs to be resolved
+        expected = ["TER      27      ARG B   4" + " " * 54,
+                    "TER      43      GLU B   6" + " " * 54,
+                    "TER      54      ALA B   7" + " " * 54,
+                    "TER      72      ASN A   1" + " " * 54,
+                    "TER      97      ARG A   2" + " " * 54,
+                    "TER     113      GLU A   3" + " " * 54,
+                    "TER     140      ARG C   5" + " " * 54,
+                    "TER     156      GLU C   2" + " " * 54,
+                    "TER     165      MET C  -1" + " " * 54,
+                    "TER     186       DT D   2" + " " * 54,
+                    "TER     188       CA A 301" + " " * 54,
+                    "TER     190      HOH A 302" + " " * 54,
+                    "TER     192      HOH A 303" + " " * 54,
+                    "TER     194      HOH B 301" + " " * 54,
+                    "TER     196      HOH C 301" + " " * 54,
+                    "TER     198      HOH C 302" + " " * 54,
+                    "TER     200      HOH C 303" + " " * 54,
+                    "TER     202      HOH C 304" + " " * 54,
+                    "TER     204      HOH C 305" + " " * 54]
+
+        self.assertEqual(ter_locations, expected)
+
+    def test_range_8(self):
+        """$ pdb_add_manual_ter -1:17:3 data/dummy.pdb"""
+
+        # Simulate input
+        sys.argv = ['', '-1:17:3', os.path.join(data_dir, 'dummy.pdb')]
+
+        # Execute the script
+        self.exec_module()
+
+        # Validate results
+        self.assertEqual(self.retcode, 0)
+        self.assertEqual(len(self.stdout), 206)
+        self.assertEqual(len(self.stderr), 0)
+
+        #add TER location asserts for dummy pdb
+
+    def test_invalid_range_1(self):
+        """$ pdb_add_manual_ter --9998:: data/add_manual_ter_test_regular.pdb"""
+
+        # Simulate input
+        sys.argv = ['', '--9998::', os.path.join(data_dir, 'add_manual_ter_test_regular.pdb')]
+
+        # Execute the script
+        self.exec_module()
+
+        # Validate results
+        self.assertEqual(self.retcode, 1)
+        self.assertEqual(len(self.stdout), 0)
+        self.assertEqual(self.stderr[0][:22],
+                         "ERROR!! Starting value")
+
+    def test_invalid_range_2(self):
+        """$ pdb_add_manual_ter -:10000: data/add_manual_ter_test_regular.pdb"""
+
+        # Simulate input
+        sys.argv = ['', '-:10000:', os.path.join(data_dir, 'add_manual_ter_test_regular.pdb')]
+
+        # Execute the script
+        self.exec_module()
+
+        # Validate results
+        self.assertEqual(self.retcode, 1)
+        self.assertEqual(len(self.stdout), 0)
+        self.assertEqual(self.stderr[0][:22],
+                         "ERROR!! Please specify")
+
+    def test_invalid_range_3(self):
+        """$ pdb_add_manual_ter -::: data/add_manual_ter_test_regular.pdb"""
+
+        # Simulate input
+        sys.argv = ['', '-:::', os.path.join(data_dir, 'add_manual_ter_test_regular.pdb')]
+
+        # Execute the script
+        self.exec_module()
+
+        # Validate results
+        self.assertEqual(self.retcode, 1)
+        self.assertEqual(len(self.stdout), 0)
+        self.assertEqual(self.stderr[0][:21],
+                         "ERROR!! Residue range")
+
+    def test_invalid_range_4(self):
+        """$ pdb_add_manual_ter -5:1:: data/add_manual_ter_test_regular.pdb"""
+
+        # Simulate input
+        sys.argv = ['', '-5:1::', os.path.join(data_dir, 'add_manual_ter_test_regular.pdb')]
+
+        # Execute the script
+        self.exec_module()
+
+        # Validate results
+        self.assertEqual(self.retcode, 1)
+        self.assertEqual(len(self.stdout), 0)
+        self.assertEqual(self.stderr[0][:21],
+                         "ERROR!! Residue range")
+
+    def test_file_not_found(self):
+        """$ pdb_add_manual_ter not_existing.pdb"""
+
+        afile = os.path.join(data_dir, 'not_existing.pdb')
+        sys.argv = ['', afile]
+
+        self.exec_module()
+
+        self.assertEqual(self.retcode, 1)  # exit code is 1 (error)
+        self.assertEqual(len(self.stdout), 0)  # nothing written to stdout
+        self.assertEqual(self.stderr[0][:22],
+                         "ERROR!! File not found")  # proper error message
+
+    def test_file_missing(self):
+        """$ pdb_add_manual_ter -1:10"""
+
+        sys.argv = ['', '-1:10']
+
+        self.exec_module()
+
+        self.assertEqual(self.retcode, 1)
+        self.assertEqual(len(self.stdout), 0)  # no output
+        self.assertEqual(self.stderr[0],
+                         "ERROR!! No data to process!")
+
+    def test_helptext(self):
+        """$ pdb_add_manual_ter"""
+
+        sys.argv = ['']
+
+        self.exec_module()
+
+        self.assertEqual(self.retcode, 1)  # ensure the program exited gracefully.
+        self.assertEqual(len(self.stdout), 0)  # no output
+        self.assertEqual(self.stderr, self.module.__doc__.split("\n")[:-1])
+
+    def test_invalid_option(self):
+        """$ pdb_add_manual_ter -A:B data/add_manual_ter_test_regular.pdb"""
+
+        sys.argv = ['', '-A:B', os.path.join(data_dir, 'add_manual_ter_test_regular.pdb')]
+
+        self.exec_module()
+
+        self.assertEqual(self.retcode, 1)
+        self.assertEqual(len(self.stdout), 0)
+        self.assertEqual(self.stderr[0][:],
+                         "ERROR!! Range values must be integers!")
+
+    def test_not_an_option(self):
+        """$ pdb_add_manual_ter 20 data/add_manual_ter_test_regular.pdb"""
+
+        sys.argv = ['', '20', os.path.join(data_dir, 'add_manual_ter_test_regular.pdb')]
+
+        self.exec_module()
+
+        self.assertEqual(self.retcode, 1)
+        self.assertEqual(len(self.stdout), 0)
+        self.assertEqual(self.stderr[0],
+                         "ERROR! First argument is not an option: '20'")
+
+
+if __name__ == '__main__':
+    from config import test_dir
+
+    mpath = os.path.abspath(os.path.join(test_dir, '..'))
+    sys.path.insert(0, mpath)  # so we load dev files before  any installation
+
+    unittest.main()