diff --git a/src/commonTest/kotlin/uk/gov/hmrc/FirstBonusTermCalculationTest.kt b/src/commonTest/kotlin/uk/gov/hmrc/FirstBonusTermCalculationTest.kt
new file mode 100644
index 0000000..300492c
--- /dev/null
+++ b/src/commonTest/kotlin/uk/gov/hmrc/FirstBonusTermCalculationTest.kt
@@ -0,0 +1,189 @@
+/*
+ * Copyright 2020 HM Revenue & Customs
+ *
+ * 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.
+ */
+package uk.gov.hmrc
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import uk.gov.hmrc.helptosavecalculator.FirstBonusTermCalculation
+import uk.gov.hmrc.helptosavecalculator.models.FirstBonusInput
+import uk.gov.hmrc.helptosavecalculator.models.YearMonthDayInput
+
+class FirstBonusTermCalculationTest {
+
+    @Test
+    fun `GIVEN calculateTotalProjectedSavingsIncludeBonuses called THEN return the total`() {
+        val valueOne = 1.0
+        val valueTwo = 2.0
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateTotalProjectedSavingsIncludeBonuses(valueOne, valueTwo)
+
+        assertEquals(3.0, result)
+    }
+
+    @Test
+    fun `GIVEN regular payment is above paid in this month WHEN calculateAdditionalSavingsThisMonth called THEN return the total`() {
+        val input = FirstBonusInput(50.0,
+                25.0,
+                25.0,
+                YearMonthDayInput(2020, 3),
+                YearMonthDayInput(2022, 2, 28),
+                YearMonthDayInput(2024, 2, 28),
+                50.0)
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateAdditionalSavingsThisMonth(input)
+
+        assertEquals(25.0, result)
+    }
+
+    @Test
+    fun `GIVEN regular payment is below paid in this month WHEN calculateAdditionalSavingsThisMonth called THEN return zero`() {
+        val input = FirstBonusInput(25.0,
+                25.0,
+                50.0,
+                YearMonthDayInput(2020, 3),
+                YearMonthDayInput(2022, 2, 28),
+                YearMonthDayInput(2024, 2, 28),
+                50.0)
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateAdditionalSavingsThisMonth(input)
+
+        assertEquals(0.0, result)
+    }
+
+    @Test
+    fun `GIVEN calculateTotalProjectedSavings called THEN return the total`() {
+        val input = FirstBonusInput(25.0,
+                25.0,
+                50.0,
+                YearMonthDayInput(2020, 3),
+                YearMonthDayInput(2022, 2, 28),
+                YearMonthDayInput(2024, 2, 28),
+                50.0)
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateTotalProjectedSavings(input, 2.0, 10)
+
+        assertEquals(277.0, result)
+    }
+
+    @Test
+    fun `GIVEN calculateTotalProjectedBonuses called THEN return the total`() {
+        val valueOne = 1.0
+        val valueTwo = 2.0
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateTotalProjectedBonuses(valueOne, valueTwo)
+
+        assertEquals(3.0, result)
+    }
+
+    @Test
+    fun `GIVEN calculateProjectedSavingsFirstBonusPeriod called THEN return the total`() {
+        val input = FirstBonusInput(25.0,
+                25.0,
+                50.0,
+                YearMonthDayInput(2020, 3),
+                YearMonthDayInput(2022, 2, 28),
+                YearMonthDayInput(2024, 2, 28),
+                50.0)
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateProjectedSavingsFirstBonusPeriod(input, 2.0, 10)
+
+        assertEquals(277.0, result)
+    }
+
+    @Test
+    fun `GIVEN balanceMustBeMoreThanForBonus is above projectedSavingsFirstBonusPeriod WHEN calculateHighestBalanceFirstBonusPeriod called THEN return balanceMustBeMoreThanForBonus`() {
+        val input = FirstBonusInput(25.0,
+                25.0,
+                50.0,
+                YearMonthDayInput(2020, 3),
+                YearMonthDayInput(2022, 2, 28),
+                YearMonthDayInput(2024, 2, 28),
+                50.0)
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateHighestBalanceFirstBonusPeriod(input, 2.0)
+
+        assertEquals(50.0, result)
+    }
+
+    @Test
+    fun `GIVEN balanceMustBeMoreThanForBonus is below projectedSavingsFirstBonusPeriod WHEN calculateHighestBalanceFirstBonusPeriod called THEN return projectedSavingsFirstBonusPeriod`() {
+        val input = FirstBonusInput(25.0,
+                25.0,
+                50.0,
+                YearMonthDayInput(2020, 3),
+                YearMonthDayInput(2022, 2, 28),
+                YearMonthDayInput(2024, 2, 28),
+                1.0)
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateHighestBalanceFirstBonusPeriod(input, 2.0)
+
+        assertEquals(2.0, result)
+    }
+
+    @Test
+    fun `GIVEN calculateProjectedFirstBonus called THEN return the total`() {
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateProjectedFirstBonus(10.0)
+
+        assertEquals(5.0, result)
+    }
+
+    @Test
+    fun `GIVEN calculateProjectedAdditionalSavingsFinalBonusPeriod called THEN return the total`() {
+        val input = FirstBonusInput(10.0,
+                25.0,
+                50.0,
+                YearMonthDayInput(2020, 3),
+                YearMonthDayInput(2022, 2, 28),
+                YearMonthDayInput(2024, 2, 28),
+                1.0)
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateProjectedAdditionalSavingsFinalBonusPeriod(input)
+
+        assertEquals(240.0, result)
+    }
+
+    @Test
+    fun `GIVEN highestBalanceFinalBonusPeriod is above highestBalanceFirstBonusPeriod WHEN calculateProjectedFinalBonus called THEN return the total`() {
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateProjectedFinalBonus(10.0, 5.0)
+
+        assertEquals(2.5, result)
+    }
+
+    @Test
+    fun `GIVEN highestBalanceFinalBonusPeriod is below highestBalanceFirstBonusPeriod WHEN calculateProjectedFinalBonus called THEN return zero`() {
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateProjectedFinalBonus(5.0, 10.0)
+
+        assertEquals(0.0, result)
+    }
+
+    @Test
+    fun `GIVEN calculateMonthsLeftInScheme called THEN return the remaining months left in scheme`() {
+        val input = FirstBonusInput(10.0,
+                25.0,
+                50.0,
+                YearMonthDayInput(2020, 3),
+                YearMonthDayInput(2022, 2, 28),
+                YearMonthDayInput(2024, 2, 28),
+                1.0)
+        val calculation = FirstBonusTermCalculation()
+        val result = calculation.calculateMonthsLeftInScheme(input)
+
+        assertEquals(Pair(47, 23), result)
+    }
+}
diff --git a/src/commonTest/kotlin/uk/gov/hmrc/FirstBonusTermCalculatorTest.kt b/src/commonTest/kotlin/uk/gov/hmrc/FirstBonusTermCalculatorTest.kt
index 2701d94..1dc47b2 100644
--- a/src/commonTest/kotlin/uk/gov/hmrc/FirstBonusTermCalculatorTest.kt
+++ b/src/commonTest/kotlin/uk/gov/hmrc/FirstBonusTermCalculatorTest.kt
@@ -18,7 +18,6 @@ package uk.gov.hmrc
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertFailsWith
-import uk.gov.hmrc.helptosavecalculator.Calculator
 import uk.gov.hmrc.helptosavecalculator.FirstBonusTermCalculator.runFirstBonusCalculator
 import uk.gov.hmrc.helptosavecalculator.exceptions.InvalidRegularPaymentException
 import uk.gov.hmrc.helptosavecalculator.models.FirstBonusInput
@@ -26,21 +25,35 @@ import uk.gov.hmrc.helptosavecalculator.models.YearMonthDayInput
 
 class FirstBonusTermCalculatorTest {
     @Test
-    fun `Throw Exception when regular payment is below 1`() {
+    fun `GIVEN regular payment is below 1 THEN InvalidRegularPaymentException thrown`() {
+        val input = FirstBonusInput(0.0,
+                0.0,
+                0.0,
+                YearMonthDayInput(2020, 3),
+                YearMonthDayInput(2022, 2, 28),
+                YearMonthDayInput(2024, 2, 28),
+                0.0)
         assertFailsWith<InvalidRegularPaymentException> {
-            Calculator.run(regularPayment = 0.0)
+            runFirstBonusCalculator(input)
         }
     }
 
     @Test
-    fun `Throw Exception when regular payment is above 50`() {
+    fun `GIVEN regular payment is above 50 THEN InvalidRegularPaymentException thrown`() {
+        val input = FirstBonusInput(51.0,
+                0.0,
+                0.0,
+                YearMonthDayInput(2020, 3),
+                YearMonthDayInput(2022, 2, 28),
+                YearMonthDayInput(2024, 2, 28),
+                0.0)
         assertFailsWith<InvalidRegularPaymentException> {
-            Calculator.run(regularPayment = 51.0)
+            runFirstBonusCalculator(input)
         }
     }
 
     @Test
-    fun `A new account with no payment AND 1 pound regular payment`() {
+    fun `GIVEN new account with no payment WHEN 1 pound regular payment added THEN correct calculation displayed`() {
         val input = FirstBonusInput(1.0,
                 0.0,
                 0.0,
@@ -60,7 +73,7 @@ class FirstBonusTermCalculatorTest {
     }
 
     @Test
-    fun `A new account with no payment AND 25 pound regular payment`() {
+    fun `GIVEN new account with no payment WHEN 25 pound regular payment added THEN correct calculation displayed`() {
         val input = FirstBonusInput(25.0,
                 0.0,
                 0.0,
@@ -80,7 +93,7 @@ class FirstBonusTermCalculatorTest {
     }
 
     @Test
-    fun `A new account with no payment AND 50 pound regular payment`() {
+    fun `GIVEN new account with no payment WHEN 50 pound regular payment added THEN correct calculation displayed`() {
         val input = FirstBonusInput(50.0,
                 0.0,
                 0.0,
@@ -100,7 +113,7 @@ class FirstBonusTermCalculatorTest {
     }
 
     @Test
-    fun `A new account paid in 50 first month, withdrawn 256 AND 25 pounds regular payment`() {
+    fun `GIVEN new account with 50 pounds first month AND withdrawn 25 WHEN 25 pound regular payment added THEN correct calculation displayed`() {
         val input = FirstBonusInput(25.0,
                 25.0,
                 50.0,